"Loch Henry" is the first Black Mirror episode located in Scotland, though the Iceland-based "Crocodile" was originally set in Scotland. "Loch Henry" was always intended to be set in Scotland; Brooker said it had an "unsentimental strand of humour" that the episode tried to draw on. The crew used Loch Lomond as a base and filmed in 18 locations, which were selected by their Scottish location scout, Liam Irving. Udo Kramer designed sets for all series six episodes. STV News reported in September 2022 that the main street of Inveraray had been adapted for filming with 1990s-style cars, bunting and signs. A scene where Pia falls into a river took place near the Falls of Falloch. Herrold said the "creepy" and "eerie atmosphere" made Pia's escape from Janet a highlight of the filming process, although she had to contend with midges in the water.

The visual effects company NVIZ worked on the montage where Davis and Pia cut a trailer for their documentary, which included adding VHS effects on footage, recreating scanning software and replicating old tabloid newspapers. The episode's soundtrack was composed by Adam Janota Bzowski and released on 21 July 2023.

Neil Armstrong of BBC Culture suggested the episode was the most disturbing of the sixth series; critics identified it as a slow-paced mystery fiction with elements of folk horror. The episode critiques true crime; according to i's Emily Baker, it reveals the genre as "pointless" and "empty". Den of Geek's Louisa Mellor wrote that it was rare for Black Mirror to give clear answers to moral questions, but that "Loch Henry" does so in its portrayal of true crime.

Davis, Pia and Stuart speak flippantly about Iain Adair's murders. A montage shows the "tonal dissonance" in their attitudes. The characters get into a car crash because they are distracted by singing a comedy song about Adair torturing his victims. Davis and Stuart are initially excited, "not disgusted or saddened", to tell Pia about the murders, according to Mellor. Pia's death can be seen as retribution for her delight in the unpleasant stories about Adair or for taking advantage of Davis's family tragedy. Like characters in the Blair Witch franchise, which is referenced in dialogue, Davis investigates a story and becomes its subject.

A red masquerade mask worn by Janet in the snuff video that Pia watches is a recurring symbol. Janet is seen putting it on again before hanging herself. Tourists in the Lochside Inn wear similar masks as costumes. The episode ends with a visual of a mask, on the BAFTA award that Davis wins. According to Vulture's Ben Rosenstock, the note that Janet leaves Davis is a "little sign of his mother's love", despite her sadism. Davis has to reinterpret his parents' love in light of their actions. Janet has a collection of Bergerac recordings—according to Marie Claire's Quinci LeGardye, the BBC detective series showcased "inoffensive crimes", making it an apt choice for a mother's favourite series.

Stuart's father Richard King owns the Lochside Inn. He objects to the documentary's creation on the grounds that it is opportunistic. This is a red herring that suggests his involvement; he had additional knowledge but did not take part in criminality. Like the Lochside Inn, Shannon Connellan of Mashable noted, establishments associated with serial killers—the Ten Bells, The Last Resort and L&L Tavern—attract tourism.

Comparisons to other series six episodes were made by critics. Streaming services such as Netflix and the fictional Streamberry—both mentioned in "Loch Henry"—are also the subject of "Joan Is Awful", in which the title character's life is adapted in real-time into a television programme. The documentary Loch Henry: Truth Will Out can be seen on Joan's Streamberry account. "Loch Henry", like "Mazey Day", criticises mass media and sees inquisitive characters led into danger by their profession. Pia is subject to racism, a central theme of "Demon 79". The episode was also seen as thematically similar to series one's "Fifteen Million Merits", which shows commodification and talent show television impacting human empathy.

Additionally, the episode makes Easter egg references to other Black Mirror events through newspapers, news tickers and BAFTA-nominated documentaries. Referenced events include: Michael Smart of "Demon 79" launching his new political party; Cooper of "Playtest" being found dead; auditions for the "Fifteen Million Merits" talent show Hot Shots opening in Australia; and a Waldo sticker on Davis's computer. Brooker highlighted as a favourite that Michael Callow of "The National Anthem" is said to run a zoo.

On the review aggregator Rotten Tomatoes, the episode holds an approval rating of 87% based on 15 reviews. Out of five stars, it was rated four stars by The Daily Telegraph, Vulture and i, 3.5 stars by Den of Geek, and three stars by The Independent. The "delicious sense of impending doom" and "pleasing wicked streak" of the episode were praised by The A.V. Club's Kayleigh Dray and Vanity Fair's Richard Lawson, respectively. Lawson summarised it a "predictable but compelling thriller" that explored the themes of "Joan Is Awful" more successfully. Rosenstock found that it told a "complete, purposeful story" with natural exposition; Alan Sepinwall, writing in Rolling Stone, found it well-paced, except for a rushed ending.

The episode's message received criticism. In The Independent, Nick Hilton summarised it as "vague, underlying commentary on the commercialisation of tragedy". Rachel Dodes of Esquire found it guilty of the "torture porn" that it attempts to criticise; Lawson did not believe its message was original. Adi Robertson wrote for The Verge that it makes "fairly mild observations" about true crime, but fans of the genre already understand its moral issues. She said it failed to explore "the potential ugliness of its premise" or create "characters who transcend it". Connellan was incredulous that Loch Henry would not have attracted true crime tourism before Davis's documentary. She suggested the episode could have further depicted the insensitivity of such tourism.

The plot twist and ending was met with mixed feedback. Despite finding the twist predictable, Paste's Leila Jordan lauded the "great Black Mirror gut punch at the end". In contrast, Robertson believed the "deliberately unsatisfying" conclusion was "rushed" and inferior to the plot twist of "White Bear". Baker was surprised by the twist, but experienced a "frustrating wait" for it. The "sad and empty" conclusion was criticised by Dodes. Rosenstock, in contrast, praised its focus on "psychological implications" for Davis rather than "cultural commentary", making it a "fascinating, haunting ending".

The acting and characterisation was widely praised. Hilton reviewed that the "sterling" cast "bring an increasing sense of unease" to the episode. Rosenstock praised the "nice chemistry" from "Stuart's brashness", "Davis's tentativeness" and "Pia's adventurous attitude", as well as these characters' humour. He found that Pia's greedy side "doesn't go too far" and lauded Herrold's performance of Pia's "horror and disbelief" at the snuff video and "barely concealed fear" in front of Janet. Ed Power, writing in The Daily Telegraph, similarly praised Pia's portrayal as "an outwardly kind person with an inner core that's all ambition" and said Blenkin "shines in the final moments" of the story. For Baker, the episode's highlights were Stuart's "gruff but likeable personality and hilarious quips". However, Robertson critiqued that Davis lacks "a strong enough presence" for his "familial drama" to have emotional impact.

Dolan's role as Janet was also praised. Power found that she "captures the duality of a person with dark depths". Rosenstock said that Dolan manages to give "weird vibes from the beginning" that make sense from a "lonely, grief-stricken widow" but suggest something deeper. Though calling Dolan "excellent", Baker criticised her Scottish accent.

"Loch Henry" received middling rankings on critics' lists of the 28 instalments of Black Mirror:

IndieWire and GamesRadar+ listed the 27 episodes, excluding Bandersnatch, where "Loch Henry" placed 13th and 25th, respectively. The New York Observer described it as the second-best of the five episodes in series six.

• "Loch Henry" at IMDb