The roster consisted of Batman, Superman, Wonder Woman, Green Lantern (John Stewart), The Flash (Wally West), Martian Manhunter, and Hawkgirl.

However, in February 2004, Cartoon Network announced a follow-up series, Justice League Unlimited, which premiered on July 31, 2004, and featured a larger roster of characters.

It is the first series in the DC Animated Universe to fully use digital ink and paint, also the first to be produced in widescreen starting in Season 2.

Alongside Kevin Conroy and George Newbern as Superman, joining the rest of the main cast is Susan Eisenberg as Wonder Woman, Maria Canals-Barrera as Hawkgirl, Phil LaMarr as John Stewart, Michael Rosenbaum as the Flash, and Carl Lumbly as Martian Manhunter.

Several actors in previous DCAU media also reprise their roles, including Dana Delany as Lois Lane, David Kaufman as Jimmy Olsen, Efrem Zimbalist Jr. as Alfred Pennyworth, Shelley Fabares and Mike Farrell as Jonathan and Martha Kent, Mark Hamill as the Joker, Clancy Brown as Lex Luthor, Corey Burton as Brainiac, Ron Perlman as Clayface, Arleen Sorkin as Harley Quinn, Peri Gilpin as Volcana, Diane Pershing as Poison Ivy, Mark Rolston as Firefly, Ted Levine as Sinestro, Brian George as Parasite, Michael Ironside as Darkseid, Michael Dorn as Kalibak, Lisa Edelstein as Mercy Graves, and Brad Garrett as Lobo.

WhatCulture praised the season for its exceptional execution, and highlighted the series' mature handling of themes such as relationships, trauma, and loss, which contributed to its broad appeal across different age groups.

[8] Den of Geek highlighted the show’s effective team dynamics, drawing a favorable comparison to Star Trek: The Next Generation for its exploration of character relationships.

[9] The Young Folks admired the show’s versatility, noting its ability to seamlessly shift between emotional, humorous, and epic moments.

[13] Oliver Sava of the AV Club countered this view by praising the expansive nature of the series and its multi-part episodes, which he felt contributed to a strong iteration of the Justice League.

[28] Dwayne McDuffie wrote the script and Andrea Romano assembled the cast, but Warner Bros. finally scrapped the project.