The season began filming in July 2019 with six days on location in Iceland. The country was chosen because the producers wanted to introduce the future of Star Trek with a place that looked different to the previous seasons, and because Kurtzman had always wanted to film there. Originally, the first two episodes of the season were to be directed by producing director Olatunde Osunsanmi and frequent Star Trek director Jonathan Frakes, respectively, but both episodes required location filming in Iceland. Osunsanmi ultimately directed both, beginning with a combined Iceland shoot, with Frakes then directing the third episode. Glen Keenan returned from the second season as the lead director of photography for the third, including serving as the cinematographer for the first two episodes. Filming locations in Iceland included the Hverfell volcano, Goðafoss waterfall, Lake Kleifarvatn, and the Blue Lagoon. The series took advantage of the Icelandic Film Commission's payback program, which reimburses 25 percent of the production costs spent in the country, receiving around US$421,480.

Filming for the rest of the season began at Pinewood Toronto Studios in Toronto, Canada, on July 18, under the working title Green Harvest. Each episode took 10 to 12 days to film on average. Frakes described the series' directing style as "shoot to thrill", with the episodic directors being encouraged to create "fabulous, intricate, complicated" shots in addition to the basic "coverage" that television directors are required to film. However, he said this was toned down for the third season compared to the previous two. In addition to Keenan, Crescenzo Notarile also served as a cinematographer for the season after working with Osunsanmi on the series Gotham. Notarile initially did not want to "rock the boat" by changing the established style of the series, which used Arri Alexa SXT cameras and Cooke Optics' Anamorphic/i Special Flare lenses. The season would often use up to four cameras at once, which made it difficult for the cinematographers to light the scenes, but Notarile felt the result made up for this by being "very visceral". The cameras were primarily on steadicam mounts, a technocrane, or a dolly cart, and often used Dutch angles, which created a style of moving and floating that the cinematographers believed would feel "Trekian". Barker's sets were specifically designed to work with the anamorphic lenses' widescreen format. Notarile soon felt confident that he could push the style of the series further with different in-camera effects, such as adding filters and prisms, using "image shakers" to safely add shaking effects to the camera, and shining a flashlight through different colored glass to distort the image. Some of the filters he used were created specifically for the season by optics company Schneider Kreuznach to give Notarile more control over lens flares. The Discovery bridge set was lit with 5000 LEDs that the cinematographers could control, including changing their color for when the ship goes into alert mode. Different lighting techniques were required for the actors wearing prosthetics and makeup: soft light from a low angle was needed for Jones's Saru prosthetics to be able to see his eyes, while Kidder was overexposed to let her green makeup "glow and blow out the imperfections".

Jon Dudkowski, one of the series' editors, made his directorial debut with the episode "Unification III". Filming for a mining colony took place at the Stelco steel plant in Hamilton, Ontario, while the planet that the Guardian of Forever appears on was filmed in an Ontario quarry. In December 2019, filming took place at the disused Kingston Penitentiary in Kingston, Ontario, to portray part of the holographic environment that Su'Kal lives in. Jones pre-recorded Saru's Kelpien singing for those scenes and lip-synced the lines on set. Filming officially wrapped in Toronto on February 24, 2020, 10 days before lockdowns began due to the COVID-19 pandemic.

Kadin stated in January 2020 that the season should be ready by that May. In late March, post-production work for the season, including editing, visual effects, and scoring, was taking place remotely due to the COVID-19 pandemic. Jon Dudkowski shared editing duties for the season with Scott Gamzon and Andrew Coutts. Their workflow involved the compiling of footage after each day of filming, working on each episode with its director for four days, and then finalizing the episodes with the showrunners. During post-production, Kurtzman brought film composer and editor John Ottman to the series to oversee the editors and help shape the episodes; Ottman had previously approached Kurtzman about the opportunity to work on Star Trek as a big fan of the franchise. In July, Paradise said the crew was "working nonstop" to complete post-production, but it was taking longer than previous seasons due to the pandemic. The editors, mixers, and color graders carried out work from their houses, with Kurtzman and Paradise supervising via Zoom. Okrand coached the actors via Skype on speaking alien languages for additional dialogue recording. The season was scheduled to premiere in October 2020, after the season finale of Star Trek: Lower Decks, and Kurtzman explained that the debut was delayed until after Lower Decks had been released because of how much longer post-production on Discovery took during the pandemic. Late in post-production, the producers added a quote to the end of the season finale from Star Trek creator Gene Roddenberry about connections. Paradise said it "felt appropriate to have something from him" due to the season's themes of connection as well as the effects of the pandemic when the season was being released.

Star Trek: Discovery was the first visual effects-heavy series to go through post-production during the pandemic. Kurtzman and Paradise reviewed visual effects shots remotely several times a week with visual effects supervisor Jason Zimmerman. Visual effects shots for each episode on Discovery typically take eight-to-ten months to complete, and this took longer for the third season during the pandemic. The season had an estimated 3500 to 5000 visual effects shots. Visual effects vendors included Pixomondo, Ghost VFX, Mackevision, Crafty Apes, DNEG, The Mill, and FX3X, as well as Zimmerman's in-house team at CBS Studios.

Since the production was unable to carry out additional photography to film pickup shots with the actors during lockdown, visual effects were used to fill these requirements. Fully computer-generated shots were created with digital doubles of the actors based on existing scans. The actors filmed motion capture performances in their houses that were then used to drive the performances of the doubles. The season required more environmental work and set extensions than the previous two, including the creation of complex holograms to augment sets. When characters are seen talking via hologram, both actors were usually filmed on set together and then a clean plate of the set without the actors was used to add transparency. Fully digital environments included the futuristic San Francisco when Discovery visits Earth and the forested homeworld of the Trills. On the latter planet, Adira enters a dream-like environment that was created digitally by Mackevision. The company animated 3D tendrils into the scene, and used a digital double of del Bario for the transition into the environment.

When adding visual effects to the environments of the first two episodes, Zimmerman made sure to retain the "true wonder" of the Iceland location shots. The parasitic ice from the second episode was created with a particle simulation by Pixomondo, who created 570 shots for the season. The company had to match their digital ice to the real glacier in Iceland. The effect of the ice forming tentacles around Discovery was difficult due to it being done near the end of Pixomondo's production schedule when time constraints limited what could be done. It ultimately required hand animation to complete rather than simulations.

Describing the season's new setting as a "double-edged sword", Zimmerman explained that they no longer had to work within the confines of established continuity but all of the new effects would still be scrutinized by fans. Discussion began early regarding how the classic Star Trek transporter effect should be depicted in this time period, and Crafty Apes created 10 to 15 different versions of what the new effect could look like. The chosen style is much faster than in previous series to show an advancement in technology. The effect of the character in "Die Trying" who was in a transporter accident was created by Ghost VFX. Other new effects include programmable matter and the fact that many chairs and consoles float. Pixomondo worked on the look of programmable matter, and initially were able to simulate it based on the movements of Book's hands on the console of his ship.

Zimmerman praised the series' art department for the different starship designs that they produced for the season, noting that they were very different from what was seen previously. Pizomondo created the sequence where Discovery arrives at Starfleet headquarters, where 15 new Starfleet ships are introduced. The headquarters environment is a "bubble forcefield generated by a corkscrew-looking space station" at its center, and Pixomondo had to track where all of the starships were inside the environment so the correct ones would always be visible for each shot. Many of the larger ships are seen moving slowly to help convey their size. Pixomondo also developed some of the non-Starfleet starships, such as Book's smaller courier ship. The biggest challenge with that ship was the fact that it can break apart and reform, with the visual effects team attempting to create logical ways for this to happen. In the season premiere, Book's ship is pursued through a debris field by another courier ship that Pixomondo also created. Some of the debris used digital models recycled from the previous seasons, but other elements had to be created new for the episode. The model of the Discovery was also reused from previous seasons, but it was upgraded to use programmable matter after a few episodes. Pixomondo developed a new process for the season's viewscreen effects, which were created in the previous seasons with 2D animation. For the upgraded Discovery model and future ships such as Book's, full 3D elements were animated and added to the shots.

The season had more digital creature work than previous seasons, including the trance worm from the premiere episode, nicknamed "Molly", which was designed by Neville Page. Ghost VFX created the worm, which was added to footage from the Iceland shoot. Ghost was also the lead vendor on "Su'Kal", contributing 130 effects shots to the episode and almost 500 for the season. "Su'Kal" required a digital environment for the holographic simulation that the title character lives in, as well as digital creature-work for the wraith-like monster that stalks him. There had been a physical version of the creature on set that was always going to be augmented with visual effects, but the team experimented with different approaches that ranged from small adjustments to completely replacing the actor with a digital version. The producers chose a solution where they would attempt to retain the on set performance but replace the actor with the "coolest and most complex" digital design. This gave them the freedom to develop the creature and the different shots as needed. The design of the creature needed to be scary, but it was also required to emote for certain story moments. The underlying muscle and skeleton system was driven by motion capture, with particle and cloth simulations layered on top that were intended to look like the creature was underwater. For a scene where the creature's mood changes from angry to calm, the "turbulence" setting of the simulation was increased to make the cloth and particles "flutter", before toning it down when the creature is calm to make the cloth appear weightless as if it is in calm water. Performance capture was used for the creature's facial expressions, which were then perfected by the visual effects artists, and Zimmerman said it was rare for the series to feature that level of nuanced, visual effects-driven creature work. Crafty Apes and DNEG also contributed to "Su'Kal", with the latter creating the Verubin Nebula digital environment.

By the end of January 2020, composer Jeff Russo had written some pre-recorded music for the season for use in the scene where Gray plays the cello for Adira. This music is heard throughout the season. Russo had not yet seen any of the completed episodes when he composed the cello music. He was "full speed ahead" composing music for the first five episodes in April 2020, working remotely due to the COVID-19 pandemic. His intention was to record the scores with an orchestra later, once it was safe to do so. A month later, Russo had begun remotely recording individual musicians from their homes. Recording engineer Michael Perfitt combined the different recordings to make them sound like the musicians were recorded together at a scoring stage, and Russo felt the result would not be of a lower quality compared to his scores for the previous seasons.

Russo said his approach to the season's music was not affected by the time-jump between seasons, stating that it still sounded like Discovery despite the new motifs he wrote for new characters (including the cat Grudge) and locations. He did state that the season would make less references to Alexander Courage's original Star Trek music and would instead make more references to Russo's own music for the first two seasons of Discovery. For example, Russo brought back his Mirror Universe music from the first season for Georgiou's storyline. Courage's theme does get played over the season finale's end credits, which Paradise said was a way of "honoring what gave birth to all of this", while Russo also referenced Jerry Goldsmith's main theme from Star Trek: Voyager when the USS Voyager-J appears. The "Andorian Opera" that is played by Aurellio near the end of the season was sung by Ayana Haviv. A soundtrack album for the season was released digitally by Lakeshore Records on April 16, 2021. All music composed by Jeff Russo:

The series was promoted at San Diego Comic-Con 2019 in a "Star Trek Universe" panel alongside other series from the franchise. The panel featured Kurtzman, Paradise, and Martin-Green, and introduced Ajala. Comic-Con also had an "immersive transporter experience" that allowed fans to "step aboard the USS Discovery and travel to strange and distant lands". The cast and crew promoted the season at further Star Trek Universe panels at New York Comic Con and PaleyFest New York in October, with a trailer revealed at the New York Comic Con panel. Several commentators questioned whether Starfleet still existed in the universe based on dialogue in the trailer. The cast and crew promoted Discovery in a virtual Star Trek Universe panel for the 2020 Comic-Con@Home convention, with a table read of the second-season finale's first act and discussion of the third season. The live stream of the event was interrupted for around 20 minutes when CBS's content protection system blocked it for copyright infringement.

The season's premiere date was announced shortly after Comic-Con@Home and was accompanied by a brief teaser depicting Burnham planting the Federation flag on a new planet. This was followed by a trailer celebrating "23 weeks of New Trek" and featuring footage from both the third season of Discovery and the first season of Lower Decks; the 23 weeks include both series, with Lower Decks premiering on August 6 and running for 10 weeks, followed the next week by the premiere of Discovery which then ran for 13 weeks. On September 8, CBS All Access streamed a free 24-hour event to celebrate the 54th anniversary of the Original Series premiere. The event included a marathon of episodes from across the Star Trek franchise, with a break during the day for a series of panels about different series. These included a panel for Discovery featuring Martin-Green, Ajala, Kurtzman, and Paradise, who debuted a full trailer for the season revealing that it was about bringing hope back to the Federation in an uncertain future. The series' new logo and the season's key art poster were also released. Another virtual Star Trek Universe panel was held for the 2020 New York Comic Con a week before the season's premiere. The cast and crew discussed the season and revealed the opening scene of the premiere. In November, ViacomCBS announced that it would donate all proceeds from a new line of Discovery-themed merchandise to GLAAD, to support the organization's "culture changing work to accelerate acceptance for LGBTQ people".

The season premiered on CBS All Access in the United States on October 15, 2020, and was released weekly for 13 episodes until January 7, 2021. Bell Media broadcast the season in Canada on CTV Sci-Fi Channel (English) and Z (French) on the same day as the U.S., before streaming episodes on Crave. Netflix released each episode for streaming in another 188 countries within 24 hours of its U.S. debut. In September 2020, ViacomCBS announced that CBS All Access would be expanded and rebranded as Paramount+ in March 2021. Existing episodes of the season remained on Paramount+ along with future seasons of the series. In November 2021, ViacomCBS announced that it had bought back the international streaming rights to Discovery from Netflix effective immediately. In August 2023, Star Trek content was removed from Crave and the season began streaming on Paramount+ in Canada. It would continue to be broadcast on CTV Sci-Fi and be available on CTV.ca and the CTV app.

The season was released on DVD, Blu-Ray, and Limited Edition Steelbook formats in the U.S. on July 20, 2021. The release includes over two hours of bonus features, including deleted scenes, a gag reel, and featurettes on the making of the season, filming in Iceland, the stunts, the bridge crew, the development of Michael Burnham's character, and Kenneth Mitchell's ALS diagnosis and role in the season. On November 2, 2021, a home media box set collecting the first three seasons of Discovery was released, with more than eight hours of special features including behind-the-scenes featurettes, deleted and extended scenes, audio commentaries, and gag reels.

Audience demand analytics company Parrot Analytics estimates streaming viewership based on global "demand expressions", with the "desire, engagement, and viewership weighted by importance". A month after the season premiered, the company said the demand for the series had "surged" to being 36.1 times more in-demand than the average United States series. Travis Clark of Business Insider said Star Trek: Discovery was certainly the most popular original series on CBS All Access, and Parrot's data placed it in third place on their weekly list of most in-demand streaming series for the week beginning November 9. The series remained in Parrot's top nine most in-demand streaming series list for each week until the one beginning December 21, and it returned to the list two weeks later (the week beginning January 4, 2021) when the season finale was released, at which point Parrot calculated the series to be 33.4 times more in-demand than the average U.S. series. In the company's list of the top 20 most in-demand streaming series of 2020, Discovery was ranked 12th and listed as 25.7 times more in-demand than the average U.S. series. It was the highest ranked CBS All Access series for the year, with the only other All Access series on the list being the first season of Star Trek: Picard (ranked 14th).

The review aggregator website Rotten Tomatoes reported a 91% approval rating for the third season, with an average rating of 7.7/10 based on 35 reviews. The website's critical consensus reads, "With less canonical baggage and a welcome dose of character development, Discovery continues to forge its own path and is narratively all the better for it." Metacritic, which uses a weighted average, assigned a score of 75 out of 100 based on reviews from 8 critics, indicating "generally favorable reviews".

Monita Mohan, looking back on the season for Collider, said a time jump within a series can be controversial, but worked in Discovery's favor; the change in setting received praise from many critics. Scott Collura at IGN described it as a reboot and felt it was likely where the first season of the series should have begun, creating a "mission statement" that he felt the series had always been missing. Alexis Gunderson of Paste agreed that the series had "finally found the story it was meant to tell", with the time jump setting up the season to be the best of the series so far with a focus on the "purest ideals of the Federation" such as the importance of connection, diplomacy, and hope. Daniel Schroeder at Slate said the season's separation from franchise staples was like watching "Star Trek: Voyager 2.0" and was "satisfyingly Trek", while Richard Edwards of GamesRadar+ felt the season was an even bolder departure from the franchise than Voyager, leaving behind so many recognizable Star Trek elements that it actually feels like a fresh start. James Whitbrook of Gizmodo found it ironic that it took moving so far into the future for the series to feel more like The Original Series, something that Jamie Lovett of ComicBook.com agreed with, saying the setting was a return to the "roots" of The Original Series, and made the Star Trek galaxy feel bigger and more dangerous than it had before. He said this was the most confident season in terms of storytelling, with a clear purpose and mission for the characters. Kayti Burt of Den of Geek praised the move for giving the series a "much-needed narrative reset" while keeping the characters from the previous seasons, and TV Insider's Matt Roush felt the new setting had enlivened the entire franchise. Devon Maloney at Vulture said the season would now succeed or fail on its own merits. Craig Elvy of Screen Rant felt it made the most of the new setting by "revel[ing] in the freedom of a fresh timeline, able to introduce planets, characters and storylines without worrying whether it'll contradict something Spock said in the 1960s". Writing for The Verge, Joshua Rivera said the season's reset would appeal to fans of the series as well as new viewers.

Alex Zalben of Decider said the characters shine and hold the season together, with the whole ensemble "hit[ting] its groove". The Daily Dot's Gavia Baker-Whitelaw felt the series had one of the best casts in the franchise, and Katie Cox at Ars Technica said the cast sold the season's story. Lacy Baugher of Den of Geek felt the main cast "gelled" during the season in a way that they did not before, attributing this to their shared experiences moving to the future, while Elvy said spending more time with the bridge crew made them more interesting. He also praised the new cast members, with the introductions of Ajala, del Barrio, and Alexander in particular being praised by many critics. Samantha Nelson of Polygon felt Adira and Gray became accessories to the relationship between Stamets and Culber, but said there was potential for a more meaningful story with the pair in the next season, while Maloney felt Adira and Gray's storyline was the highlight of the season, saying, "If any storyline calls for Discovery's signature Feelings™ treatment, it's the one about lost, lonely ghost kids finding a family". Zalben and Cox both praised Saru's role, with Cox specifically calling out Jones's ability to portray Saru through the prosthetics. Martin-Green received praise from many critics for her performance, but Zack Handlen at The A.V. Club criticized the fact that the series continued to revolve around Burnham, and both Nelson and Maloney felt Saru was sidelined by the season to allow for Burnham's character development. Baugher said there was a sense of inevitability regarding Burnham becoming captain of the Discovery, and Edwards said the whole series had been building to that moment. He criticized the fact that Burnham effectively becomes a superhero to save the day almost on her own, with help from a deus ex machina ending. Maloney said he wanted to celebrate Burnham's promotion to captain, but felt it happened without her growing as a character or learning from her mistakes. In contrast, Elvy said Burnham had developed into a better protagonist by the end of the season, retaining her rebellious side while becoming more vulnerable and accessible to the audience.

Christian Blauvelt of IndieWire and Burt both said the season was the best looking of the series, especially praising the work of Osunsanmi and the Iceland locations for the first two episodes, and Blauvelt felt it could be the best looking of the franchise as a whole. Matthew Carey Salyer, writing for Forbes, compared the new production design to Blade Runner, while several reviewers drew comparisons to Star Wars. Sam Thielman at The Guardian was positive about this, highlighting the fun that is added by the Star Wars-esque "double-crosses, shootouts and ramshackle spaceships" in the season. Several critics compared Book to the Star Wars character Han Solo, while Edwards felt the alien characters looked more like Star Wars aliens than Star Trek ones. Cox was more critical, describing the setting as a "network-safe" version of the Mad Max franchise. Baker-Whitelaw did not think the design was advanced enough to realistically be 900 years beyond the setting of the first two seasons. She felt the initial depiction of a "generic cyberpunk city with neon holograms and black leather costumes" would fit within Star Trek: Picard. Collura criticized the Emerald Chain as uninteresting villains for the season. Elvy agreed that they would not go down as classic characters, but felt they allowed the season to explore more episodic stories than if it had a more imposing villain.

Critics discussed the season's parallels with the real world, something that Lovett said was done by all the best Star Trek series. He compared the lack of dilithium to the dwindling supply of fossil fuels in the modern world. Collura said it was a "thinly veiled analog for our own state of being", while Salyer said the season was a "striking reflection of our common social isolation over the past year". Burt said Star Trek gives hope that real-world problems can be solved and this was especially welcome during the COVID-19 pandemic and the 2020 United States presidential election. Maloney agreed, stating, "Not to be dramatic, but the world really needs Star Trek to be great right now." Thielman said the season was the most thoughtful of the series so far, and Melanie McFarland from Salon felt it showed how to carry on from adversity, which was appropriate following the 2016 United States presidential election. Collura said the secret behind the Burn being the grief of a child was a great concept, as did Edwards who thought it was a "classic Trek twist". Authors and commentators Tom Fitzgerald and Lorenzo Marquez felt the series understood what Star Trek was about more than some of its detractors gave it credit for, but criticized its continued focus on emotional characters over science, diplomacy, and problem-solving. Handlen also criticized the series' reliance on emotional moments and felt the season was "pretty much the same show we left behind in season two, for better and worse". Several critics felt the season's conflicts were given too-easy solutions. Both Pat Brown at Slant Magazine and Cox criticized it as taking the "safe" options, and Brown said it would be more in the spirit of Star Trek to move on from the Federation than try to restore it. Baker-Whitelaw was critical of the "one-note political issues" and their representation as a "tiresome season-wide arc about saving the galaxy", while Collura questioned what the season actually revealed about the loss of hope and stated: "Right now things seem worse than ever in the real world, while all Discovery's problems were solved in 13 episodes flat". Nelson said the writers had introduced complex storylines and ideas and then wrapped them up with "feel-good simplicity", undermining the exploration of key ideas such as resource scarcity, colonialism, trauma, the burdens of leadership, and gender identity. In contrast, Whitbrook said the theme of hope was a "bright, consistent core" throughout the season, something that the first two seasons were missing in his opinion, and he praised how the characters were rewarded at the end of the season for having hope. He said this proved that modern incarnations of Star Trek could still have the "simple, optimistic core" of early franchise iterations. Baugher also felt the season affirmed its central messages by the end.

The season is one of 117 television series that received the ReFrame Stamp for the years 2020 to 2021. The stamp is awarded by the gender equity coalition ReFrame as a "mark of distinction" for film and television projects that are proven to have gender-balanced hiring, with stamps being awarded to projects that hire female-identifying people, especially women of color, in four out of eight critical areas of their production.

• Star Trek: Discovery season 3 at IMDb
• Star Trek: Discovery season 3 at Memory Alpha