Neanderthals had more robust and stockier builds than typical modern humans, wider and barrel-shaped rib cages; wider pelvises; and proportionally shorter forearms and forelegs.

Based on 45 Neanderthal long bones from 14 men and 7 women, the average height was 164 to 168 cm (5 ft 5 in to 5 ft 6 in) for males and 152 to 156 cm (5 ft 0 in to 5 ft 1 in) for females. For comparison, the average height of 20 males and 10 females Upper Palaeolithic humans is, respectively, 176.2 cm (5 ft 9.4 in) and 162.9 cm (5 ft 4.1 in), although this decreases by 10 cm (4 in) nearer the end of the period based on 21 males and 15 females; and the average in the year 1900 was 163 cm (5 ft 4 in) and 152.7 cm (5 ft 0 in), respectively. The fossil record shows that adult Neanderthals varied from about 147.5 to 177 cm (4 ft 10 in to 5 ft 10 in) in height, although some may have grown much taller (73.8 to 184.8 cm based on footprint length and from 65.8 to 189.3 cm based on footprint width). For Neanderthal weight, samples of 26 specimens found an average of 77.6 kg (171 lb) for males and 66.4 kg (146 lb) for females. Using 76 kg (168 lb), the body mass index for Neanderthal males was calculated to be 26.9–28.2, which in modern humans correlates to being overweight. This indicates a very robust build. The Neanderthal LEPR gene concerned with storing fat and body heat production is similar to that of the woolly mammoth, and so was likely an adaptation for cold climate.

The neck vertebrae of Neanderthals are thicker from the front to the rear and transversely than those of (most) modern humans, leading to stability, possibly to accommodate a different head shape and size. Although the Neanderthal thorax (where the ribcage is) was similar in size to modern humans, the longer and straighter ribs would have equated to a widened mid-lower thorax and stronger breathing in the lower thorax, which are indicative of a larger diaphragm and possibly greater lung capacity. The lung capacity of Kebara 2 was estimated to have been 9.04 L (2.39 US gal), compared to the average human capacity of 6 L (1.6 US gal) for males and 4.7 L (1.2 US gal) for females. The Neanderthal chest was also more pronounced (expanded front-to-back, or antero-posteriorly). The sacrum (where the pelvis connects to the spine) was more vertically inclined, and was placed lower in relation to the pelvis, causing the spine to be less curved (exhibit less lordosis) and to fold in on itself somewhat (to be invaginated). In modern populations, this condition affects just a proportion of the population, and is known as a lumbarised sacrum. Such modifications to the spine would have enhanced side-to-side (mediolateral) flexion, better supporting the wider lower thorax. It is claimed by some that this feature would be normal for all Homo, even tropically-adapted Homo ergaster or erectus, with the condition of a narrower thorax in most modern humans being a unique characteristic.

Body proportions are usually cited as being "hyperarctic" as adaptations to the cold, because they are similar to those of human populations which developed in cold climates—the Neanderthal build is most similar to that of Inuit and Siberian Yupiks among modern humans—and shorter limbs result in higher retention of body heat. Nonetheless, Neanderthals from more temperate climates—such as Iberia—still retain the "hyperarctic" physique. In 2019, English anthropologist John Stewart and colleagues suggested Neanderthals instead were adapted for sprinting, because of evidence of Neanderthals preferring warmer wooded areas over the colder mammoth steppe, and DNA analysis indicating a higher proportion of fast-twitch muscle fibres in Neanderthals than in modern humans. He explained their body proportions and greater muscle mass as adaptations to sprinting as opposed to the endurance-oriented modern human physique, as persistence hunting may only be effective in hot climates where the hunter can run prey to the point of heat exhaustion (hyperthermia). They had longer heel bones, reducing their ability for endurance running, and their shorter limbs would have reduced moment arm at the limbs, allowing for greater net rotational force at the wrists and ankles, causing faster acceleration. In 1981, American palaeoanthropologist Erik Trinkaus made note of this alternate explanation, but considered it less likely.

Neanderthals had less developed chins, sloping foreheads, and longer, broader, more projecting noses. The Neanderthal skull is typically more elongated, but also wider, and less globular than that of most modern humans, and features much more of an occipital bun, or "chignon", a protrusion on the back of the skull, although it is within the range of variation for modern humans who have it. It is caused by the cranial base and temporal bones being placed higher and more towards the front of the skull, and a flatter skullcap.

The Neanderthal face is characterised by subnasal as well as mid-facial prognathism, where the zygomatic arches are positioned in a rearward location relative to modern humans, while their maxillary bones and nasal bones are positioned in a more forward direction, by comparison. Neanderthal eyeballs are larger than those of modern humans. One study proposed that this was due to Neanderthals having enhanced visual abilities, at the expense of neocortical and social development. However, this study was rejected by other researchers who concluded that eyeball size does not offer any evidence for the cognitive abilities of Neanderthal or modern humans.

The projected Neanderthal nose and paranasal sinuses have generally been explained as having warmed air as it entered the lungs and retained moisture ("nasal radiator" hypothesis); if their noses were wider, it would differ to the generally narrowed shape in cold-adapted creatures, and that it would have been caused instead by genetic drift. Also, the sinuses reconstructed wide are not grossly large, being comparable in size to those of modern humans. However, if sinus size is not an important factor for breathing cold air, then the actual function would be unclear, so they may not be a good indicator of evolutionary pressures to evolve such a nose. Further, a computer reconstruction of the Neanderthal nose and predicted soft tissue patterns shows some similarities to those of modern Arctic peoples, potentially meaning the noses of both populations convergently evolved for breathing cold, dry air.

Neanderthals featured a rather large jaw which was once cited as a response to a large bite force evidenced by heavy wearing of Neanderthal front teeth (the "anterior dental loading" hypothesis), but similar wearing trends are seen in contemporary humans. It could also have evolved to fit larger teeth in the jaw, which would better resist wear and abrasion, and the increased wear on the front teeth compared to the back teeth probably stems from repetitive use. Neanderthal dental wear patterns are most similar to those of modern Inuit. The incisors are large and shovel-shaped, and, compared to modern humans, there was an unusually high frequency of taurodontism, a condition where the molars are bulkier due to an enlarged pulp (tooth core). Taurodontism was once thought to have been a distinguishing characteristic of Neanderthals which lent some mechanical advantage or stemmed from repetitive use, but was more likely simply a product of genetic drift. The bite force of Neanderthals and modern humans is now thought to be about the same, about 285 N (64 lbf) and 255 N (57 lbf) in modern human males and females, respectively.

The Neanderthal braincase averages 1,640 cm (100 cu in) for males and 1,460 cm (89 cu in) for females, which is significantly larger than the averages for all groups of extant humans; for example, modern European males average 1,362 cm (83.1 cu in) and females 1,201 cm (73.3 cu in). For 28 modern human specimens from 190,000 to 25,000 years ago, the average was about 1,478 cm (90.2 cu in) disregarding sex, and modern human brain size is suggested to have decreased since the Upper Palaeolithic. The largest Neanderthal brain, Amud 1, was calculated to be 1,736 cm (105.9 cu in), one of the largest ever recorded in hominids. Both Neanderthal and human infants measure about 400 cm (24 cu in).

When viewed from the rear, the Neanderthal braincase has lower, wider, rounder appearance than in anatomically modern humans. This characteristic shape is referred to as "en bombe" (bomb-like), and is unique to Neanderthals, with all other hominid species (including most modern humans) generally having narrow and relatively upright cranial vaults, when viewed from behind. The Neanderthal brain would have been characterised by relatively smaller parietal lobes and a larger cerebellum. Neanderthal brains also have larger occipital lobes (relating to the classic occurrence of an occipital bun in Neanderthal skull anatomy, as well as the greater width of their skulls), which implies internal differences in the proportionality of brain-internal regions, relative to Homo sapiens, consistent with external measurements obtained with fossil skulls. Their brains also have larger temporal lobe poles, wider orbitofrontal cortex, and larger olfactory bulbs, suggesting potential differences in language comprehension and associations with emotions (temporal functions), decision making (the orbitofrontal cortex) and sense of smell (olfactory bulbs). Their brains also show different rates of brain growth and development. Such differences, while slight, would have been visible to natural selection and may underlie and explain differences in the material record in things like social behaviours, technological innovation and artistic output.

The lack of sunlight most likely led to the proliferation of lighter skin in Neanderthals; however, it has been recently claimed that light skin in modern Europeans was not particularly prolific until perhaps the Bronze Age. Genetically, BNC2 was present in Neanderthals, which is associated with light skin colour; however, a second variation of BNC2 was also present, which in modern populations is associated with darker skin colour in the UK Biobank. DNA analysis of three Neanderthal females from southeastern Europe indicates that they had brown eyes, dark skin colour and brown hair, with one having red hair.

In modern humans, skin and hair colour is regulated by the melanocyte-stimulating hormone—which increases the proportion of eumelanin (black pigment) to phaeomelanin (red pigment)—which is encoded by the MC1R gene. There are five known variants in modern humans of the gene which cause loss-of-function and are associated with light skin and hair colour, and another unknown variant in Neanderthals (the R307G variant) which could be associated with pale skin and red hair. The R307G variant was identified in a Neanderthal from Monti Lessini, Italy, and possibly Cueva del Sidrón, Spain. However, as in modern humans, red was probably not a very common hair colour because the variant is not present in many other sequenced Neanderthals.

Maximum natural lifespan and the timing of adulthood, menopause and gestation were most likely very similar to modern humans. However, it has been hypothesised, based on the growth rates of teeth and tooth enamel, that Neanderthals matured faster than modern humans, although this is not backed up by age biomarkers. The main differences in maturation are the atlas bone in the neck as well as the middle thoracic vertebrae fused about 2 years later in Neanderthals than in modern humans, but this was more likely caused by a difference in anatomy rather than growth rate.

Generally, models on Neanderthal caloric requirements report significantly higher intakes than those of modern humans because they typically assume Neanderthals had higher basal metabolic rates (BMRs) due to higher muscle mass, faster growth rate and greater body heat production against the cold; and higher daily physical activity levels (PALs) due to greater daily travelling distances while foraging. However, using a high BMR and PAL, American archaeologist Bryan Hockett estimated that a pregnant Neanderthal would have consumed 5,500 calories per day, which would have necessitated a heavy reliance on big game meat; such a diet would have caused numerous deficiencies or nutrient poisonings, so he concluded that these are poorly warranted assumptions to make.

Neanderthals may have been more active during dimmer light conditions rather than broad daylight because they lived in regions with reduced daytime hours in the winter, hunted large game (such predators typically hunt at night to enhance ambush tactics), and had large eyes and visual processing neural centres. Genetically, colour blindness (which may enhance mesopic vision) is typically correlated with northern-latitude populations, and the Neanderthals from Vindija Cave, Croatia, had some substitutions in the Opsin genes which could have influenced colour vision. However, the functional implications of these substitutions are inconclusive. Neanderthal-derived alleles near ASB1 and EXOC6 are associated with being an evening person, narcolepsy and day-time napping.

Neanderthals suffered a high rate of traumatic injury, with an estimated 79–94% of specimens showing evidence of healed major trauma, of which 37–52% were severely injured, and 13–19% injured before reaching adulthood. One extreme example is Shanidar 1, who shows signs of an amputation of the right arm likely due to a nonunion after breaking a bone in adolescence, osteomyelitis (a bone infection) on the left clavicle, an abnormal gait, vision problems in the left eye, and possible hearing loss (perhaps swimmer's ear). In 1995, Trinkaus estimated that about 80% succumbed to their injuries and died before reaching 40, and thus theorised that Neanderthals employed a risky hunting strategy ("rodeo rider" hypothesis). However, rates of cranial trauma are not significantly different between Neanderthals and Middle Palaeolithic modern humans (although Neanderthals seem to have had a higher mortality risk), there are few specimens of both Upper Palaeolithic modern humans and Neanderthals who died after the age of 40, and there are overall similar injury patterns between them. In 2012, Trinkaus concluded that Neanderthals instead injured themselves in the same way as contemporary humans, such as by interpersonal violence. A 2016 study looking at 124 Neanderthal specimens argued that high trauma rates were instead caused by animal attacks, and found that about 36% of the sample were victims of bear attacks, 21% big cat attacks, and 17% wolf attacks (totalling 92 positive cases, 74%). There were no cases of hyena attacks, although hyenas still nonetheless probably attacked Neanderthals, at least opportunistically. Such intense predation probably stemmed from common confrontations due to competition over food and cave space, and from Neanderthals hunting these carnivores.

Low population caused a low genetic diversity and probably inbreeding, which reduced the population's ability to filter out harmful mutations (inbreeding depression). However, it is unknown how this affected a single Neanderthal's genetic burden and, thus, if this caused a higher rate of birth defects than in modern humans. It is known, however, that the 13 inhabitants of Sidrón Cave collectively exhibited 17 different birth defects likely due to inbreeding or recessive disorders. Likely due to advanced age (60s or 70s), La Chapelle-aux-Saints 1 had signs of Baastrup's disease, affecting the spine, and osteoarthritis. Shanidar 1, who likely died at about 30 or 40, was diagnosed with the most ancient case of diffuse idiopathic skeletal hyperostosis (DISH), a degenerative disease which can restrict movement, which, if correct, would indicate a moderately high incident rate for older Neanderthals.

Neanderthals were subject to several infectious diseases and parasites. Modern humans likely transmitted diseases to them; one possible candidate is the stomach bacteria Helicobacter pylori. The modern human papillomavirus variant 16A may descend from Neanderthal introgression. A Neanderthal at Cueva del Sidrón, Spain, shows evidence of a gastrointestinal Enterocytozoon bieneusi infection. The leg bones of the French La Ferrassie 1 feature lesions that are consistent with periostitis—inflammation of the tissue enveloping the bone—likely a result of hypertrophic osteoarthropathy, which is primarily caused by a chest infection or lung cancer. Neanderthals had a lower cavity rate than modern humans, despite some populations consuming typically cavity-causing foods in great quantity, which could indicate a lack of cavity-causing oral bacteria, namely Streptococcus mutans.

Two 250,000-year-old Neanderthaloid children from Payré, France, present the earliest known cases of lead exposure of any hominin. They were exposed on two distinct occasions either by eating or drinking contaminated food or water, or inhaling lead-laced smoke from a fire. There are two lead mines within 25 km (16 mi) of the site.

Neanderthals likely lived in more sparsely distributed groups than contemporary modern humans, but group size is thought to have averaged 10 to 30 individuals, similar to modern hunter-gatherers. Reliable evidence of Neanderthal group composition comes from Cueva del Sidrón, Spain, and the footprints at Le Rozel, France: the former shows 7 adults, 3 adolescents, 2 juveniles and an infant; whereas the latter, based on footprint size, shows a group of 10 to 13 members where juveniles and adolescents made up 90%.

A Neanderthal child's teeth analysed in 2018 showed it was weaned after 2.5 years, similar to modern hunter gatherers, and was born in the spring, which is consistent with modern humans and other mammals whose birth cycles coincide with environmental cycles. Indicated from various ailments resulting from high stress at a low age, such as stunted growth, British archaeologist Paul Pettitt hypothesised that children of both sexes were put to work directly after weaning; and Trinkaus said that, upon reaching adolescence, an individual may have been expected to join in hunting large and dangerous game. However, the bone trauma is comparable to modern Inuit, which could suggest a similar childhood between Neanderthals and contemporary modern humans. Further, such stunting may have also resulted from harsh winters and bouts of low food resources.

Sites showing evidence of no more than three individuals may have represented nuclear families or temporary camping sites for special task groups (such as a hunting party). Bands likely moved between certain caves depending on the season, indicated by remains of seasonal materials such as certain foods, and returned to the same locations generation after generation. Some sites may have been used for over 100 years. Cave bears may have greatly competed with Neanderthals for cave space, and there is a decline in cave bear populations starting 50,000 years ago onwards (although their extinction occurred well after Neanderthals had died out). Neanderthals also had a preference for caves whose openings faced towards the south. Although Neanderthals are generally considered to have been cave dwellers, with 'home base' being a cave, open-air settlements near contemporaneously inhabited cave systems in the Levant could indicate mobility between cave and open-air bases in this area. Evidence for long-term open-air settlements is known from the 'Ein Qashish site in Israel, and Moldova I in Ukraine. Although Neanderthals appear to have had the ability to inhabit a range of environments—including plains and plateaux—open-air Neanderthals sites are generally interpreted as having been used as slaughtering and butchering grounds rather than living spaces.

In 2022, remains of the first-known Neanderthal family (six adults and five children) were excavated from Chagyrskaya Cave in the Altai Mountains of southern Siberia in Russia. The family, which included a father, a daughter, and what appear to be cousins, most likely died together, presumably from starvation.

Neanderthals, like contemporaneous modern humans, were most likely polygynous, based on their low second-to-fourth digit ratios, a biomarker for prenatal androgen effects that corresponds to high incidence of polygyny in haplorhine primates.

Canadian ethnoarchaeologist Brian Hayden calculated a self-sustaining population that avoids inbreeding to consist of about 450–500 individuals, which would necessitate these bands to interact with 8–53 other bands, but more likely the larger estimate given low population density. Analysis of the mtDNA of the Neanderthals of Cueva del Sidrón, Spain, showed that the three adult men belonged to the same maternal lineage, while the three adult women belonged to different ones. This suggests a patrilocal residence (that a woman moved out of her group to live with her partner). However, the DNA of a Neanderthal from Denisova Cave, Russia, shows that she had an inbreeding coefficient of 1⁄8 (her parents were either half-siblings with a common mother, double first cousins, an uncle and niece or aunt and nephew, or a grandfather and granddaughter or grandmother and grandson) and the inhabitants of Cueva del Sidrón show several defects, which may have been caused by inbreeding or recessive disorders.

Considering most Neanderthal artefacts were sourced no more than 5 km (3.1 mi) from the main settlement, Hayden considered it unlikely these bands interacted very often, and mapping of the Neanderthal brain and their small group size and population density could indicate that they had a reduced ability for inter-group interaction and trade. However, a few Neanderthal artefacts in a settlement could have originated 20, 30, 100 and 300 km (12.5, 18.5, 60 and 185 mi) away. Based on this, Hayden also speculated that macro-bands formed which functioned much like those of the low-density hunter-gatherer societies of the Western Desert of Australia. Macro-bands collectively encompass 13,000 km (5,000 sq mi), with each band claiming 1,200–2,800 km (460–1,080 sq mi), maintaining strong alliances for mating networks or to cope with leaner times and enemies. Similarly, British anthropologist Eiluned Pearce and Cypriot archaeologist Theodora Moutsiou speculated that Neanderthals were possibly capable of forming geographically expansive ethnolinguistic tribes encompassing upwards of 800 people, based on the transport of obsidian up to 300 km (190 mi) from the source compared to trends seen in obsidian transfer distance and tribe size in modern hunter-gatherers. However, according to their model Neanderthals would not have been as efficient at maintaining long-distance networks as modern humans, probably due to a significantly lower population. Hayden noted an apparent cemetery of six or seven individuals at La Ferrassie, France, which, in modern humans, is typically used as evidence of a corporate group which maintained a distinct social identity and controlled some resource, trading, manufacturing and so on. La Ferrassie is also located in one of the richest animal-migration routes of Pleistocene Europe.

Genetic analysis indicates there were at least three distinct geographical groups—Western Europe, the Mediterranean coast, and east of the Caucasus—with some migration among these regions. Post-Eemian Western European Mousterian lithics can also be broadly grouped into three distinct macro-regions: Acheulean-tradition Mousterian in the southwest, Micoquien in the northeast, and Mousterian with bifacial tools (MBT) in between the former two. MBT may actually represent the interactions and fusion of the two different cultures. Southern Neanderthals exhibit regional anatomical differences from northern counterparts: a less protrusive jaw, a shorter gap behind the molars, and a vertically higher jawbone. These all instead suggest Neanderthal communities regularly interacted with neighbouring communities within a region, but not as often beyond.

Nonetheless, over long periods of time, there is evidence of large-scale cross-continental migration. Early specimens from Mezmaiskaya Cave in the Caucasus and Denisova Cave in the Siberian Altai Mountains differ genetically from those found in Western Europe, whereas later specimens from these caves both have genetic profiles more similar to Western European Neanderthal specimens than to the earlier specimens from the same locations, suggesting long-range migration and population replacement over time. Similarly, artefacts and DNA from Chagyrskaya and Okladnikov Caves, also in the Altai Mountains, resemble those of eastern European Neanderthal sites about 3,000–4,000 km (1,900–2,500 mi) away more than they do artefacts and DNA of the older Neanderthals from Denisova Cave, suggesting two distinct migration events into Siberia. Neanderthals seem to have suffered a major population decline during MIS 4 (71–57,000 years ago), and the distribution of the Micoquian tradition could indicate that Central Europe and the Caucasus were repopulated by communities from a refuge zone either in eastern France or Hungary (the fringes of the Micoquian tradition) who dispersed along the rivers Prut and Dniester.

There is also evidence of inter-group conflict: a skeleton from La Roche à Pierrot, France, showing a healed fracture on top of the skull apparently caused by a deep blade wound, and another from Shanidar Cave, Iraq, found to have a rib lesion characteristic of projectile weapon injuries.

It is sometimes suggested that, since they were hunters of challenging big game and lived in small groups, there was no sexual division of labour as seen in modern hunter-gatherer societies. That is, men, women and children all had to be involved in hunting, instead of men hunting with women and children foraging. However, with modern hunter-gatherers, the higher the meat dependency, the higher the division of labour. Further, tooth-wearing patterns in Neanderthal men and women suggest they commonly used their teeth for carrying items, but men exhibit more wearing on the upper teeth, and women the lower, suggesting some cultural differences in tasks.

It is controversially proposed that some Neanderthals wore decorative clothing or jewellery—such as a leopard skin or raptor feathers—to display elevated status in the group. Hayden postulated that the small number of Neanderthal graves found was because only high-ranking members would receive an elaborate burial, as is the case for some modern hunter-gatherers. Trinkaus suggested that elderly Neanderthals were given special burial rites for lasting so long given the high mortality rates. Alternatively, many more Neanderthals may have received burials, but the graves were infiltrated and destroyed by bears. Given that 20 graves of Neanderthals aged under 4 have been found—over a third of all known graves—deceased children may have received greater care during burial than other age demographics.

Looking at Neanderthal skeletons recovered from several natural rock shelters, Trinkaus said that, although Neanderthals were recorded as bearing several trauma-related injuries, none of them had significant trauma to the legs that would debilitate movement. He suggested that self worth in Neanderthal culture derived from contributing food to the group; a debilitating injury would remove this self-worth and result in near-immediate death, and individuals who could not keep up with the group while moving from cave to cave were left behind. However, there are examples of individuals with highly debilitating injuries being nursed for several years, and caring for the most vulnerable within the community dates even further back to H. heidelbergensis. Especially given the high trauma rates, it is possible that such an altruistic strategy ensured their survival as a species for so long.

Neanderthals were once thought of as scavengers, but are now considered to have been apex predators. In 1980, it was hypothesised that two piles of mammoth skulls at La Cotte de St Brelade, Jersey, at the base of a gulley were evidence of mammoth drive hunting (causing them to stampede off a ledge), but this is contested. Living in a forested environment, Neanderthals were likely ambush hunters, getting close to and attacking their target—a prime adult—in a short burst of speed, thrusting in a spear at close quarters. Younger or wounded animals may have been hunted using traps, projectiles, or pursuit. Some sites show evidence that Neanderthals slaughtered whole herds of animals in large, indiscriminate hunts and then carefully selected which carcasses to process. Nonetheless, they were able to adapt to a variety of habitats. They appear to have eaten predominantly what was abundant within their immediate surroundings, with steppe-dwelling communities (generally outside of the Mediterranean) subsisting almost entirely on meat from large game, forest-dwelling communities consuming a wide array of plants and smaller animals, and waterside communities gathering aquatic resources, although even in more southerly, temperate areas such as the southeastern Iberian Peninsula, large game still featured prominently in Neanderthal diets. Contemporary humans, in contrast, seem to have used more complex food extraction strategies and generally had a more diverse diet. Nonetheless, Neanderthals still would have had to have eaten a varied enough diet to prevent nutrient deficiencies and protein poisoning, especially in the winter when they presumably ate mostly lean meat. Any food with high contents of other essential nutrients not provided by lean meat would have been vital components of their diet, such as fat-rich brains, carbohydrate-rich and abundant underground storage organs (including roots and tubers), or, like modern Inuit, the stomach contents of herbivorous prey items.

For meat, Neanderthals appear to have fed predominantly on hoofed mammals. They primarily consumed red deer and reindeer, as these two were the most abundant game; however, they also ate other Pleistocene megafauna such as chamois, ibex, wild boar, steppe wisent, aurochs, Irish elk, woolly mammoth, straight-tusked elephant, woolly rhinoceros, Merck's rhinoceros the narrow-nosed rhinoceros, wild horse, and so on. There is evidence of directed cave and brown bear hunting both in and out of hibernation, as well as butchering. Analysis of Neanderthal bone collagen from Vindija Cave, Croatia, shows nearly all of their protein needs derived from animal meat. Some caves show evidence of regular rabbit and tortoise consumption. At Gibraltar sites, there are remains of 143 different bird species, many ground-dwelling such as the common quail, corn crake, woodlark, and crested lark. Scavenging birds such as corvids and eagles were commonly exploited. Neanderthals also exploited marine resources on the Iberian, Italian and Peloponnesian Peninsulas, where they waded or dived for shellfish, as early as 150,000 years ago at Cueva Bajondillo, Spain, similar to the fishing record of modern humans. At Vanguard Cave, Gibraltar, the inhabitants consumed Mediterranean monk seal, short-beaked common dolphin, common bottlenose dolphin, Atlantic bluefin tuna, sea bream and purple sea urchin; and at Gruta da Figueira Brava, Portugal, there is evidence of large-scale harvest of shellfish, crabs and fish. Evidence of freshwater fishing was found in Grotte di Castelcivita, Italy, for trout, chub and eel; Abri du Maras, France, for chub and European perch; Payré, France; and Kudaro Cave, Russia, for Black Sea salmon.

Edible plant and mushroom remains are recorded from several caves. Neanderthals from Cueva del Sidrón, Spain, based on dental tartar, likely had a meatless diet of mushrooms, pine nuts and moss, indicating they were forest foragers. Remnants from Amud Cave, Israel, indicates a diet of figs, palm tree fruits and various cereals and edible grasses. Several bone traumas in the leg joints could possibly suggest habitual squatting, which, if the case, was likely done while gathering food. Dental tartar from Grotte de Spy, Belgium, indicates the inhabitants had a meat-heavy diet including woolly rhinoceros and mouflon sheep, while also regularly consuming mushrooms. Neanderthal faecal matter from El Salt, Spain, dated to 50,000 years ago—the oldest human faecal matter remains recorded—show a diet mainly of meat but with a significant component of plants. Evidence of cooked plant foods—mainly legumes and, to a far lesser extent, acorns—was discovered at the Kebara Cave site in Israel, with its inhabitants possibly gathering plants in spring and fall and hunting in all seasons except fall, although the cave was probably abandoned in late summer to early fall. At Shanidar Cave, Iraq, Neanderthals collected plants with various harvest seasons, indicating they scheduled returns to the area to harvest certain plants, and that they had complex food-gathering behaviours for both meat and plants.

Neanderthals probably could employ a wide range of cooking techniques, such as roasting, and they may have been able to heat up or boil soup, stew, or animal stock. The abundance of animal bone fragments at settlements may indicate the making of fat stocks from boiling bone marrow, possibly taken from animals that had already died of starvation. These methods would have substantially increased fat consumption, which was a major nutritional requirement of communities with low carbohydrate and high protein intake. Neanderthal tooth size had a decreasing trend after 100,000 years ago, which could indicate an increased dependence on cooking or the advent of boiling, a technique that would have softened food.

At Cueva del Sidrón, Spain, Neanderthals likely cooked and possibly smoked food, as well as used certain plants—such as yarrow and camomile—as flavouring, although these plants may have instead been used for their medicinal properties. At Gorham's Cave, Gibraltar, Neanderthals may have been roasting pinecones to access pine nuts.

At Grotte du Lazaret, France, a total of twenty-three red deer, six ibexes, three aurochs, and one roe deer appear to have been hunted in a single autumn hunting season, when strong male and female deer herds would group together for rut. The entire carcasses seem to have been transported to the cave and then butchered. Because this is such a large amount of food to consume before spoilage, it is possible these Neanderthals were curing and preserving it before winter set in. At 160,000 years old, it is the oldest potential evidence of food storage. The great quantities of meat and fat which could have been gathered in general from typical prey items (namely mammoths) could also indicate food storage capability. With shellfish, Neanderthals needed to eat, cook, or in some manner preserve them soon after collection, as shellfish spoils very quickly. At Cueva de los Aviones, Spain, the remains of edible, algae eating shellfish associated with the alga Jania rubens could indicate that, like some modern hunter gatherer societies, harvested shellfish were held in water-soaked algae to keep them alive and fresh until consumption.

Competition from large Ice Age predators was rather high. Cave lions likely targeted horses, large deer and wild cattle; and leopards primarily reindeer and roe deer; which heavily overlapped with Neanderthal diet. To defend a kill against such ferocious predators, Neanderthals may have engaged in a group display of yelling, arm waving, or stone throwing; or quickly gathered meat and abandoned the kill. However, at Grotte de Spy, Belgium, the remains of wolves, cave lions and cave bears—which were all major predators of the time—indicate Neanderthals hunted their competitors to some extent.

Neanderthals and cave hyenas may have exemplified niche differentiation, and actively avoided competing with each other. Although they both mainly targeted the same groups of creatures—deer, horses and cattle—Neanderthals mainly hunted the former and cave hyenas the latter two. Further, animal remains from Neanderthal caves indicate they preferred to hunt prime individuals, whereas cave hyenas hunted weaker or younger prey, and cave hyena caves have a higher abundance of carnivore remains. Nonetheless, there is evidence that cave hyenas stole food and leftovers from Neanderthal campsites and scavenged on dead Neanderthal bodies. Similarly, evidence from the site of Payre in southern France shows that Neanderthals exhibited resource partitioning with wolves.

There are several instances of Neanderthals practising cannibalism across their range. The first example came from the Krapina, Croatia site, in 1899, and other examples were found at Cueva del Sidrón and Zafarraya in Spain; and the French Grotte de Moula-Guercy, Les Pradelles, and La Quina. For the five cannibalised Neanderthals at the Grottes de Goyet, Belgium, there is evidence that the upper limbs were disarticulated, the lower limbs defleshed and also smashed (likely to extract bone marrow), the chest cavity disembowelled, and the jaw dismembered. There is also evidence that the butchers used some bones to retouch their tools. The processing of Neanderthal meat at Grottes de Goyet is similar to how they processed horse and reindeer. About 35% of the Neanderthals at Marillac-le-Franc, France, show clear signs of butchery, and the presence of digested teeth indicates that the bodies were abandoned and eaten by scavengers, likely hyaenas.

These cannibalistic tendencies have been explained as either ritual defleshing, pre-burial defleshing (to prevent scavengers or foul smell), an act of war, or simply for food. Due to a small number of cases, and the higher number of cut marks seen on cannibalised individuals than animals (indicating inexperience), cannibalism was probably not a very common practice, and it may have only been done in times of extreme food shortages as in some cases in recorded human history.

Neanderthals used ochre, a clay earth pigment. Ochre is well documented from 60 to 45,000 years ago in Neanderthal sites, with the earliest example dating to 250–200,000 years ago from Maastricht-Belvédère, the Netherlands (a similar timespan to the ochre record of H. sapiens). It has been hypothesised to have functioned as body paint, and analyses of pigments from Pech de l'Azé, France, indicates they were applied to soft materials (such as a hide or human skin). However, modern hunter gatherers, in addition to body paint, also use ochre for medicine, for tanning hides, as a food preservative, and as an insect repellent, so its use as decorative paint for Neanderthals is speculative. Containers apparently used for mixing ochre pigments were found in Peștera Cioarei, Romania, which could indicate modification of ochre for solely aesthetic purposes.

Neanderthals collected uniquely shaped objects and are suggested to have modified them into pendants, such as a fossil Aspa marginata sea snail shell possibly painted red from Grotta di Fumane, Italy, transported over 100 km (62 mi) to the site about 47,500 years ago; three shells, dated to about 120–115,000 years ago, perforated through the umbo belonging to a rough cockle, a Glycymeris insubrica, and a Spondylus gaederopus from Cueva de los Aviones, Spain, the former two associated with red and yellow pigments, and the latter a red-to-black mix of hematite and pyrite; and a king scallop shell with traces of an orange mix of goethite and hematite from Cueva Antón, Spain. The discoverers of the latter two claim that pigment was applied to the exterior to make it match the naturally vibrant inside colouration. Excavated from 1949 to 1963 from the French Grotte du Renne, Châtelperronian beads made from animal teeth, shells and ivory were found associated with Neanderthal bones, but the dating is uncertain and Châtelperronian artefacts may actually have been crafted by modern humans and simply redeposited with Neanderthal remains.

Gibraltarian palaeoanthropologists Clive and Geraldine Finlayson suggested that Neanderthals used various bird parts as artistic media, specifically black feathers. In 2012, the Finlaysons and colleagues examined 1,699 sites across Eurasia, and argued that raptors and corvids, species not typically consumed by any human species, were overrepresented and show processing of only the wing bones instead of the fleshier torso, and thus are evidence of feather plucking of specifically the large flight feathers for use as personal adornment. They specifically noted the cinereous vulture, red-billed chough, kestrel, lesser kestrel, alpine chough, rook, jackdaw and the white tailed eagle in Middle Palaeolithic sites. Other birds claimed to present evidence of modifications by Neanderthals are the golden eagle, rock pigeon, common raven and the bearded vulture. The earliest claim of bird bone jewellery is a number of 130,000-year-old white tailed eagle talons found in a cache near Krapina, Croatia, speculated, in 2015, to have been a necklace. A similar 39,000-year-old Spanish imperial eagle talon necklace was reported in 2019 at Cova Foradà in Spain, though from the contentious Châtelperronian layer. In 2017, 17 incision-decorated raven bones from the Zaskalnaya VI rock shelter, Ukraine, dated to 43–38,000 years ago were reported. Because the notches are more-or-less equidistant to each other, they are the first modified bird bones that cannot be explained by simple butchery, and for which the argument of design intent is based on direct evidence.

Discovered in 1975, the so-called Mask of la Roche-Cotard, a mostly flat piece of flint with a bone pushed through a hole on the midsection—dated to 32, 40, or 75,000 years ago—has been purported to resemble the upper half of a face, with the bone representing eyes. It is contested whether it represents a face, or if it even counts as art. In 1988, American archaeologist Alexander Marshack speculated that a Neanderthal at Grotte de L'Hortus, France, wore a leopard pelt as personal adornment to indicate elevated status in the group based on a recovered leopard skull, phalanges and tail vertebrae.