Vandal Savage forms the Legion of Doom to destroy the Justice League using proactive measures created by Batman should the JLA ever go rogue.
- Kevin Conroy as Bruce Wayne/Batman
- Tim Daly as Clark Kent/Superman
- Susan Eisenberg as Diana Prince/Wonder Woman
- Nathan Fillion as Hal Jordan/Green Lantern
- Carl Lumbly as J'onn J'onnz/John Jones/Martian Manhunter and Ma'alefa'ak
- Michael Rosenbaum as Barry Allen/The Flash
- Olivia d'Abo as Carol Ferris/Star Sapphire
- Phil Morris as Vandar Adg/Vandal Savage
- Bumper Robinson as Victor Stone/Cyborg
- Claudia Black as Barbara Ann Minerva/Cheetah
- Danny Kaufman as Jimmy Olsen
- Alexis Denisof as Sam Scudder/Mirror Master
- Paul Blackthorne as John Corben/Metallo
- Carlos Alazraqui as Bane
- Jim Meskimen as King of the Royal Flush Gang
- Grey DeLisle as Queen of the Royal Flush Gang, Lois Lane
- Robin Atkin Downes as Jack of the Royal Flush Gang, Alfred Pennyworth
- Juliet Landau as Ten of the Royal Flush Gang
- Bruce Timm as Ace of the Royal Flush Gang
- Danny Jacobs as Special Agent Porter
- Dee Bradley Baker as Officer In Charge
- Brian George as The Mayor
- Steven Blum - Miner
- Keith Szarabajka - Henry Ackerson
- Andrea Romano - Voice of the Batcomputer
Differences between comic and filmEdit
- None of the villains in the fim were featured in the story arc, with Vandal Savage's Legion of Doom substituting for Ra's al Ghul's League of Assassins.
- Aquaman and Plastic Man, both of whom were in the Tower of Babel story arc, are the only members of the JLA in the comic arc that are not in the film. Cyborg is also the only film member of the JLA that was not in the story arc.
- The Barry Allen and Hal Jordan versions of The Flash and Green Lantern were used in lieu of the Wally West and Kyle Rayner versions used in the comics respectively.
- The methods of killing the heroes also varied in the film.
- Martian Manhunter was poisoned and set on fire by Ma'alefa'ak, rather than shot with burning nano mites by Talia al Ghul.
- Star Sapphire attempted to break Green Lantern's will using the Scarecrow's fear gas; Kyle Rayner was blinded using a post-hypnotic suggestion in the comics. The use of the Scarecrow's fear gas was the same method used to kill Aquaman.
- Batman was lured to his parent's graves by Bane taking their bodies, the same method Ra's used to distract Batman. However, Bane then attempted to bury Batman alive.
- Superman was shot in the chest with a Kryptonite bullet by Metallo; in the comics his cells overloaded due to Red Kryptonite radiation.
- Wonder Woman was infected with nanites by the Cheetah that made everyone look and sound like Cheetah herself in hopes Wonder Woman's heart would give out by fighting an army of Cheetahs; in the comics the League of Assassins put her in a virtual reality fighting a challenger equal to her, again in hope of a heart attack.
- Mirror Master planted a bomb in The Flash's wrist that would activate should Flash attempt to remove it, do nothing or (should he run, which he did) slowed down; in the comics he was shot in the neck with a vibrating bullet, giving him seizures at light speed.
- Both The Flash and Green Lantern had radically different contingency plans. Neither Batman or Superman had plans for their deaths in the actual story arc.
- The plot bears similarities to a brief story arc in Action Comics featuring the Anti-Justice League, in which the alien Queen Bee formed the Anti-Justice League, allying herself with a specific villain best suited to defeat a specific member of the JLA (i.e. Clayface to Batman, Brainiac to Superman). Vandal Savage replaces Queen Bee in the film, and the Legion is made up of more obscure antagonists (i.e. Star Sapphire to Green Lantern instead of Sinestro, Metallo to Superman instead of Brainiac). Vandal Savage himself organized a similar foil to the Teen Titans named Tartarus.
- The movie was adapted and written by Dwayne McDuffie shortly before his death in February 2011 and is dedicated to his memory.
- Kevin Conroy, Tim Daly, Susan Eisenberg, Carl Lumbly, Michael Rosenbaum, Phil Morris, Danny Kaufman, and Alexis Denisof are all reprising roles from the DC animated universe, while Nathan Fillion is reprising his role from Green Lantern: Emerald Knights. Juliet Landau, Brian George, Bruce Timm, Andrea Romano, and Dee Bradley Baker, all of whom have voiced characters in the DC animated universe, are the only voice actors featured who are not reprising a role from the DCAU.