The series is based on the second campaign of the actual play web series Critical Role and is set 20 years after the events of The Legend of Vox Machina, on the continent of Wildemount east of Tal'Dorei.

The project traces its origins to a 2018 sponsorship deal between Critical Role and D&D Beyond, which produced an animated ad spot featuring the Mighty Nein characters; this ad 'opened doors' for The Legend of Vox Machina to be produced, which in turn led to this series.

The show was announced in January 2023 alongside a first-look deal between Critical Role Productions and Amazon Studios, with Critical Role continuing to produce under its banner, Metapigeon.

Matthew Mercer, Critical Role's dungeon master, reprises his 'Hidden Matt Mercer' tradition from The Legend of Vox Machina by voicing Essek Thelyss as well as various background characters, with the rest of the main cast also voicing one-off characters.

Taliesin Jaffe expressed gratitude that the animated series would allow exploration of Mollymauk Tealeaf's backstory, since the character died early in the original tabletop campaign.

Sam Riegel said his character Nott the Brave was, in part, created to 'reflect the trans experience.'

Voice acting for the series had begun by June 8, 2024, and by June 2025 the cast had recorded the entirety of both the first and second seasons.

Showrunner Tasha Huo said the production tried to treat the show like a live-action series, aiming for more mature, elevated storytelling and more drama than The Legend of Vox Machina, including the deliberate decision to kill off characters who had survived in the original campaign to establish a darker tone.

Art director Joseph Martinez said that unlike the high-fantasy look of The Legend of Vox Machina, The Mighty Nein's setting is more grounded and based on Eastern European history, going for a brutalist architectural look that 'over encumbers' the characters, with deliberate color cues signaling political tensions and characters' states of mind.

Polygon noted the irony that the group is called the Mighty Nein despite there not actually being nine members, a joke that was referenced in the SDCC 2025 panel clip pointing out there are only seven adventurers.

The first season holds a 100% approval rating on Rotten Tomatoes from 22 critic reviews and a Metacritic score of 80 out of 100 based on 7 critics, indicating generally favorable reviews.