Greg Weisman attributed the show's return to the existence of streaming services, particularly Netflix, where the show garnered high viewings. Executive producer Sam Register reportedly said that both Weisman and Brandon Vietti had created "the perfect binge-watching show five years too soon". Weisman posited that Young Justice might not have been cancelled if the model of binge-watching had been mainstream when the show was still on the air. Additionally, Brandon Vietti cited the power of social media, which grew exponentially since the show's cancellation, and the paramount role it played in allowing fans to have their voices heard.
Weisman claimed that he and Vietti were told about the show's return circa ten days before it was officially announced. However, he admitted to not being entirely surprised, because they had talked to Sam Register a year before and the chances of the show returning seemed higher. Vietti japed that "the time jump between season one and two worked so well in the story, [they] wanted to do it in real life".
Production on the series commenced on November 14, 2016, while voice recording purportedly began around April 2017 and was completed in May 2018. The season was finalized on April 10, 2019 making up two years, fours months and 27 days to complete all 26 episodes.
Regarding the changes in the writing process, Vietti observed that, on a streaming service, they are no longer restricted by the Broadcast Standards and Practices, as they were on Cartoon Network. He went on to say that, while they have no intention of changing the show dramatically, now they have more "creative room to progress into more adult themes and storylines", which reconciles with the nature of the show. However, he guaranteed that the show won't become a "swear" or a "gore fest".
For Greg Weisman, the biggest difference has been the lack of the three-act structure, because on a streaming service there are no commercial breaks in the episodes. He noted that despite still using it mostly by force of habit, this new paradigm sometimes changes the way they work.
Since production was announced, Warner Bros. has imposed an "info-embargo" on the show, which prohibits everyone involved from talking about it. The only public statement about the show came from Greg Weisman, when he revealed that the third season would "play off of stuff" from the previous seasons, as well as the companion comics.
On April 25, 2017 an official press release announced the title of the season, along with a plot summary:
"In the highly anticipated new season, the team faces its greatest challenge yet as it takes on meta-human trafficking and the terrifying threat it creates for a society caught in the crossfire of a genetic arms race spanning the globe and the galaxy."
On the same day, Brandon Vietti tweeted a pithier logline: "The Team battles meta-human trafficking to protect a society caught in the crossfire of a genetic arms race."
On July 21, 2017 at San Diego Comic-Con, Greg Weisman, Brandon Vietti and Phil Bourassa revealed new designs for old characters, and unveiled three new ones: Arrowette, Thirteen and Spoiler. They also announced that the season would comprise 26 episodes, ten of which had been recorded and another 12 were in progress. The final four episodes hadn't been written yet, but Weisman stated that they knew where they are going with them. Moreover, Brandon Vietti confirmed that there would be another time jump of unspecified length between seasons, because in order "to really delve into a character's story, you need to jump a little forward in time sometimes". Greg Weisman also offered some insight into the overall plot:
"Since the Reach in season two sort of revealed the Meta-Gene, everyone is getting into the act—first world nations, third world nations, rogue nations, corporations, aliens from outer space. Everyone wants to weaponize the human race and meta-human trafficking is the major thing that our characters are dealing with this season."
Without going into specifics, Weisman hinted that the season would feature some elements from the current DC ComicsRebirth run. Finally, in a post-panel interview, Weisman revealed that Bash Bashford, a very obscure character from old Superboy comics, would debut in season three.
On July 20, there was another panel at San Diego Comic-Con with Greg Weisman, Brandon Vietti, Phil Bourassa, Jamie Thomason, Stephanie Lemelin and Troy Baker, who was revealed to be voicing one of those new characters: Brion Markov, aka Geo-Force. Vietti and Weisman also revealed the names of two other characters from the artwork, Forager and Halo, and their respective voice actors, Jason Spisak and Zehra Fazal. Weisman also revealed that, at that point, seven episodes were completed and ready for release.
As of early September 2018, twelve episodes were completed and ready for release. On October 4, during the DC Universe panel at New York Comic Con 2018, Geoff Johns announced that Young Justice: Outsiders would be split into two blocks of 13 episodes, with three new episodes debuting weekly from January to February and June to July 2019. He also announced a one-shot prequel comic to accompany the show, with Greg Weisman and Christopher Jones back as writer and artist, respectfully. Weisman clarified that said issue will tell one story set between season two and season three and hinted that if many people read it, then they could be committed for more stories.
Young Justice: Outsiders was originally expected to debut in the fourth quarter of 2018 on DC Universe, but on June 28 it was reported to debut in 2019.
According to Parrot Analytics, during the week following the premiere of Young Justice: Outsiders, the series debuted at no. 4 in the Top 10 shows on streaming services with 28 million "Demand Expressions", a proprietary metric used by Parrot Analytics to measure global demand for TV content. The following week, after the release of the fourth, fifth and sixth episodes, the series climbed to no. 1 and then dropped to no. 6 in the subsequent week.
The review aggregation website Rotten Tomatoes reported a 100% approval rating right after the release of the first three episodes, a rating still maintained after the first half of the season was released, with an average rating of 4.5/5. The site's consensus states: " The next generation of DC heroes and villains return with sharper animation and a bloodier sensibility that nevertheless retains the preceding seasons' hefty dose of heart."