• Ripster (voiced by Lee Tockar) - John Bolton is the smartest the leader and oldest of the four brothers who enjoys creating inventions. He has taken up most of his knowledge and skills from his father. He is also an avid poolplayer. In the first episode of the show, John rides a motorbike. When transformed into Ripster, he becomes a great white shark able to bite through steel.
  • Jab (voiced by Matt Hill) - Clint Bolton is the laziest of the Street Sharks, but enjoys boxing and appears to have some talent with mechanics. When transformed into Jab, he becomes a hammerhead shark and uses his head as a battering ram.
  • Streex (voiced by Andrew Rannells) - Robert "Bobby" Bolton Jr. is a level-headed, cool and self-proclaimed ladies' man. He is always shown wearing his rollerblades and appears to enjoy parachuting and snowboarding and later plays drums professionally. When transformed into Streex, he becomes a tiger shark, named after the purple streaks on his body. In episodes 1-3, he was originally called "Blades" for his skills as a rollerblader.
  • Big Slammu (voiced by D. Kevin Williams) - Coop Bolton is the strongest and youngest of the four. He is also a football player in high school. In the first episode, he uses a skateboard. When transformed into Big Slammu, he becomes a whale shark and his most prominent maneuver is the "Seismic Slam" in which he may shake or crack the ground with his fists.
  • Dr. Robert Bolton (voiced by D. Kevin Williams) - A university professor and the father of the Bolton Brothers who invents the gene-manipulation device for peaceful uses. He is only seen on-screen in the first episode where he tries to stop Dr. Paradigm's experiments only to become changed into an unseen inhuman creature. Afterward, he is only ever represented by a shadow cast on the wall. It is suggested through the series that Dr. Bolton secretly assists his sons. The episode "Shark Source" shows him defeating Dr. Piranoid to rescue a kidnapped mutant crocodile. Despite the fact that he helps them, Dr. Bolton is never reunited with his sons.
  • Sir Thomas Bolton - An ancestor of the protagonists who is encountered in the episode "Sir Shark-a-Lot". He is the target of Paradigm's time-travel excursion to destroy the Bolton family.