- Brainiac 5 (Adam Wylie)- He is the best character on the show, in my option. He is portrayed as having little emotion, but not being heartless at the same time. In the show Brainiac 5 is an android able to transform his body. He is also the youngest and the smartest, thanks to his 12th level intelligence. His design is based off of his descent Brainiac (Corey Burton). However unlike Brainiac, he idolizes Superman. Episode 4 implies "normal" Coluans (?), Brainiac 5's race, have a hive mind and disapprove of his desire to be more "human".
- Superman (Yuri Lowenthal)- He is really Superboy, but due legal issues the show had to call him Superman. He is very similar to his "Smallvile" television-self: he's just mastering his powers and this is "before" he moved to Metropolis.
- Lighting Lad (Andy Milder)- He is the hot shot-leader, until Bouncing Boy becomes leader in episode 11. When he creates lighting his scar glows. He acts like a jerk alot. He lost his arm to Imperiex (Phil Morris) and got it replace with a robotic one. He has a relationship with Saturn Girl.
- Saturn Girl (Kari Wahlgren)- She is a tough girl, unlike her early comic-self. She has seemly unlimited telepathy.
- Bouncing Boy (Michael Cornacchia)- He acts like the "Bones" to Brainiac 5's "Spock". In this verison he turns into a ball instead of just more round. He is very good pilot and became leader in the 11th episode, although this doesn't appear to be the case for season 2. In episode 4, it's revealed he's seen alot of horror movies.
- Triplet Girl (Kari Wahlgren)- She is able to turn herself into 3 semi-separate-mind bodies. While she is one person her dress and hair has purple, white and orange in it, but when they separate they each get 1 of these colors for her dress and hair. She shows affection for Bouncing Boy, a nod to their comic marriage. In season 2, she become the Duo Damsel, after Imperiex murder her "white-self". But she regained her white-self at the end of Season 2.
- Timber Wolf (Shawn Harrison)- Thanks to his father (?*), he is a human-wolf ceature with enhanced speed, agility, senses and strength. Although he acts like a tough guy, it's revealed he likes to bake. He seems to have feeling for Phantom Girl (see Phantom Girl) and vise versa.
- Phantom Girl (Heather Hogan)- James Tucker, the show's animator, says she is "a princess who is kind of spoiled, but ultimately very devoted to being in the Legion. She has a somewhat sarcastic attitude to cover the fact that she really gets a kick out of finally being with other kids like herself." Like her comic counterpart, she can fly and become temporally intangible. When she goes though machines, unlike her comic counterpart, they breakdown. She seems to have feelings for Timber Wolf.
- Chameleon Boy (Alexander Polinsky)- He is the only core member that only appears in the second season. He has high-scale shapeshifting, allowing him to transform into almost anything and gain the thing's strength in the process. His father, R. J. Brande (Lex Lang), is rich and funds the Legion.
- Comsic Boy (Will Wheaton)- He is the former leader of the legion, becomes leader agin in season 2. He his magentic power are the same as his comic conterpart. He seems to dislike Lighting Lad. He first appears in episode #8.
Legion of Super Heroes episodes Episode #1, 4, 6 and 9