Four young mutant turtle brothers; Leonardo, Raphael, Donatello, and Michelangelo, goes on the surface world where they encounter their new human friends, April O'Neil and Casey Jones, and numerous enemies, such as, the Foot Clan, the Purple Dragons, Krang, the Rat King, Dr. Baxter Stockman, and many others while both having a lots of adventures in the city of New York City and uncover the mysterious, yet somewhat both dark and strange secrets of their mutation as well!
- Leonardo/"Leo": The leader of the team who's the bravest, loyalest, adventurous, enthusiastic, fearless, benevolent, and noble, yet cool, calm, and collected, eldest and most mature of the four who can be serious of his leadership skills at times, wear a blue mask and wield a pair of katana blades. Voiced by Will Friedle.
- Raphael/"Raph": The team's second-in-command and second oldest of the four who's often can be hot-headed at times and always has his brothers calm him down and also like listening to calm music as well to help calm himself down and has a friendly rivalry with Leo, wear a red mask and wield a pair of tonfa. Voiced by Scott Porter.
- Donatello/"Donny": The team's brains who's the middlest and a serious hacker and often speaks in technobubble and also having a natural aptitude for both science and technology who often make catchphares, which his choices are, mosty, quite perplexing when he and his brothers are celebrating their victories, wear a dark purple mask and wield a bo staff. Voiced by James Arnold Taylor.
- Michelangelo/"Micky": The youngest of the four who's has a gentle heart and can really get emotionally at times who enjoys eating pizza, drawing, thanks to his creative imagination, training, and watching movies on his spear time, wear a orange mask and wield a kusari-fundo. Voiced by Drake Bell.
- Master Splinter: A mutant rat who's the sensei and father-figure of the turtles, who learn in martial arts by his owner, Hamato Yoshi, before he was killed by the Shredder. He can be protective of them at times and often show to be a expert martial artist when he fighting any enemies, he also give them advise of how to beat a enemy or trust each other at times. Voiced by Phil LaMarr.
- April O'Neil: A young 19-year old college student who's work as a pizza delivery, which is why the turtles, even Micky, love pizza, after quitting her former job as Baxter's apprentice after uncover her boss' dark secrets. Voiced by Laura Bailey.
- Casey Jones: April's 20-year old friend, roommate, and brother-figure who wear a hocky mask to fight crimes and help the turtles, he become friend to Raph, despite his age. He also has a grudge with Hun for killing his father when he was twelve. Voiced by Travis Willingham.
- Kirby O'Neil: April's father who's can be a bit protective of her at times, but does love her well while also having a hard time of trusting the Turtles at times. Voiced by Diedrich Bader.
- Keno: April's friend and partner who's deliver pizza like her, he quickly become friends with the Turtles after being saved by them and Casey, he also start taking martial art class to help out his friends. Voiced by Andrew Kishino.
- Professor Jordan Perry: April and Casey's science teacher who's rather very mysterious and hide a mysterious secret from them. Voiced by Tom Kenny.
- Irma Langinstein: April's next door roommate and best friend who's both shy and witty who's see April as her only friend. Voiced by Catherine Taber.
- Vernon Fenwick: Casey's friend and April's friendly rival who's often seek to be one step ahead of April at times, but often somewhat fail at times and even like hanging with Casey at times as well. Voiced by Rob Paulsen.
- Oroku Saki/Shredder: The evil, diabolical, power-hungry, serious-minded, dangerous, deadliest, cruel, and cold head leader of the Foot Clan, he previously killed Splinter's master, Hamato Yoshi, seventeen years ago. He's seek to destroy the turtles once he uncover their existence. Voiced by Steven Blum.
- Tatsu: Shredder's right-hand man and Hun's rival who use martial arts skills to fight against his enemies when in battles. He often train future Foot ninjas of how to train. Voiced by John DiMaggio.
- Dr. Baxter Stockman: A scientist who's secretly a criminal mastermind who's was the former boss of April, who try to kills once she uncover his secrets who also help of hiding the Foot Clan. Voiced by Khary Payton.
- Foot Ninjas: Shredder's foot soldiers who's often wield numerous ninja weapons and always remain silent.
- Hun: Leader of the Purple Dragons who's responsible for killing Casey's father, Tatsu's rival, and loyal to the Shredder. Voiced by Clancy Brown.
- Dragon Face: The Purple Dragons' second-in-command who's very loyal to Hun and seek to make himself worthy to Hun, at times. Voiced by .
- John: The third-in-command of the Purple Dragons who's rebellious, hot-headed, cocky, and headstrong, yet somewhat curious who's also wield both a staff and a sledgehammer. Voiced by .
- Mohawk: A member of the Purple Dragons with a tall dark purple mohawk hair who's often both curious and a total goofball, at times, and wield three weapons, a baseball bat, a dagger, and a nunchuck. Voiced by Quentin Flynn.
- Two Ton: A heavyset member of the Purple Dragons who's loyal but clumsy and dim-witted. Voiced by Bill Fagerbakke.
- Krang: An brain-like alien being
Producers: Greg Weisman,
Directors: Michael Chang, Sebastian Montes, Dave Bullock, Jennifer Coyle, Marty Isenberg, Jamie Vickers, Brendan Clogher
Voice Director: Lisa Schaffer
Music by: Noam Kaniel
Animation Provided by:
Production Companies: Nickelodeon Animation Studio
- Nickelodeon & Nicktoon (USA)
- Teletoon (Canada)
- TV Asahi (Japan)
- TV-Y7-FV (USA)