Grojband

• Corey Jaron Riffin (voiced by Lyon Smith) – Corey is the younger brother of Trina Riffin. He is a 13-year-old confident, optimistic, laidback, and quirky leader, vocalist, and guitarist of Grojband. Although good-natured, he is on a constant search for new gigs for the band to perform at and will do whatever it takes to play music at them, which is usually by angering his sister, Trina, who will write in her diary. He then translates her venting into lyrics for their songs due to the fact he is unable to come up with lyrics of his own. He is named after the Canadian musician Corey Crewe.^[4]
• Laney Penn (voiced by Bryn McAuley) – Laney is the bassist, Vocalist and self-proclaimed band manager of Grojband. She is the younger sister of Chloe. Laney is a short, sarcastic, ambitious, and passionate redhead and the only female in the band, the latter of which everyone else isn't able to acknowledge.^[5] She tends to be the most rational member of the band, mainly because she cares about the others, but is usually prone to giving in to Corey and his schemes. This is because she has a crush on Corey, to which Corey is oblivious to. Her name is a pun on the famous Beatles song Penny Lane.^[6]
• Kin Kujira (voiced by Sergio Di Zio) – Kin is the Japanese keyboardist of the band, and Kon's small, bespectacled older twin brother and best friend. Despite his eccentric behaviour and antics, he is extremely smart and has a knack for advanced technology, often building strange gadgets that help the band with their gigs.^[7]
• Kon Kujira (voiced by Tim Beresford) – Kon is the Japanese drummer of the band, and Kin's large, overweight younger twin brother and best friend. Kon is sometimes dense and just as crazy as his brother Kin, but is very strong, usually well-meaning, and has a cherubic and excitable demeanor. He and his brother derive their first names from King Kong and their last name from Gojira, the Japanese name for Godzilla.^[7]

The Newmans

The Newmans are a gender-reversed doppelgänger band to Grojband. They are Grojband's rivals and always compete with them for different gigs or in contests. They are named after the character Newman from Seinfeld. Their voice actors are the same as the original Grojband.^[8]

• Carrie Beff – Corey's doppelgänger: a stuck-up, shallow girl who is the leader, guitarist, and vocalist of The Newmans. She is also Mina's younger sister. As seen throughout the show, Corey and Carrie are bitter enemies, as one would love to see the other go down. However, both have shown a slight tolerance for each other, and will work together if the situation calls for it.
• Larry (Lenny) Nepp – Laney's gender-bent rival: bassist and band manager of The Newmans. Similar to Laney, Larry has a visible crush on Carrie, Corey's gender-warped rival, as seen in one episode. He isn't as courageous as her, though.
• Kim Kagami – Kin's gender-bent rival, who is also the keyboardist of The Newmans. When Grojband and the Newmans fused together in one episode, Kin fused with Kim and both showed some jealousy against their respective twin for being such great friends with each other.
• Konnie Kagami – Kon's gender-bent rival, who is also the drummer of The Newmans. In one episode, it is shown that under certain circumstances, Kon and Konnie are able to get along.

Others

• Katrina "Trina" Riffin (voiced by Alyson Court) – Trina is Corey's 16-year-old sister. She is mean, cruel, self-centered, and always determined to make Corey's life miserable. She is the series' main antagonist and constantly tries to ruin Grojband's gigs. Whenever she is overcome with emotion (usually anger, sometimes love/happiness, fear, or sadness), she impulsively writes her diary in a dramatic manner, which provides Grojband with the lyrical inspiration they need for their songs. She has a crush on the cute neighborhood boy, Nick Mallory, who doesn't give her the time of day.^[9][10] Her full first name is Katrina, and she was kind with others at one point in her life. She is named after the late Canadian musician Trina Crewe.
• Bernadette "Mina" Beff (voiced by Denise Oliver) – Mina is a timid, naive, and bespectacled 16-year-old girl who thinks is Trina's best friend, but in reality, she is more like her slave. Although much nicer than Trina, she wishes to be as cool as Trina, and does whatever she tells her to do. Her real name is Bernadette, but Trina forced her to legally change it so their names would rhyme. She is also Carrie's older sister. Her last name is a pun on the phrase "BFF", or "Best Friends Forever".^[11] In the series finale, after Trina abandoned her to be destroyed by the meteor, Mina finally snaps and stands up to Trina and scolds her for everything she went through for her so-called friend.
• Nick Mallory (voiced by Graeme Cornies) – Nick is an extremely cool and handsome 16-year-old boy, whom all the girls in school adore, especially Trina. He is sometimes referred to as "Hunky Nick Mallory" by Trina and many others around him. He always refers to himself in the third person, but isn't inherently antagonistic, and will sometimes aid the band when they see use of him. He has a little brother named Mick Mallory who looks and acts just like him. He is named after Nick Moore and Mallory Keaton, two characters from the sitcom Family Ties.^[12]
• Kate Persky and Allie Day (voiced by Addison Holley and Madelyn May respectively) – Allie and Kate are Grojband's 9-year-old groupies and their biggest (and possibly, only) fans. They are head over heels in love with Corey, and are willing to do anything for him, but they can be creepy and obsessive at times. They are named after the title characters of the sitcom Kate & Allie, while their last names come from Bill Persky and Linda Day, the directors of the aforementioned series.
• Mayor Mellow (voiced by Kedar Brown) – The diminutive mayor of Peaceville, who is always seen carrying a picture of his mother around, and speaks in rhymes. He is well-intentioned and wants what is best for his town, but his ways to do it are questionable and often extreme. He also has a somewhat short fuse, and he jumps to the conclusion too soon at times. In "The Pirate Lounge for Me", Mellow is revealed to have been a former lounge singer known as Melodious Monk.^[13]
• Buzz Newsworthy and Chance Happening (voiced by Dwayne Hill and Julie Lemieux respectively) – The news anchors of the Peaceville News. They are quick on the scene to cover important news events. However they have a habit of exaggerating the stories. They also sometimes have feuds over who is more proficient.

Recurring

• Barney (voiced by Rob Tinkler) – A very rich billionaire who owns multiple businesses around Peaceville. He is always addressed by the name of the business in front of his real name: such as while he works at the salad restaurant he is referred to as "Salad Barney", or at the coffee house he is referred to as "Bean Barney".
• Party Danimal (voiced by Christian Potenza) – The school party critic who first appeared in the episode "Pox N' Roll", he rates other people's parties with a score out of "10 Awesomes".
• Captain Tighty Whitey (voiced by Rob Tinkler) – A pirate captain who enjoys stealing things from people and finding treasure. He first appeared in the episode "On the Air and Out to Sea".
• G'ORB (voiced by Rob Tinkler) – An evil alien space orb who is bent on destroying the world. He is the leader of a band called The Orb Experience, made up of three other space orbs named T'ORB, Z'ORB, and N'ORB. He first appeared in the episode "Space Jammin'" where he challenged Grojband to a battle of the bands and lost. He was only a minor one-time character with the rest of the band until he returned in the season 1 finale episode "Hear Us Rock Part 2", where he returned and challenged Grojband to a rematch and threatened to destroy the world with an apocalyptic meteor if they lost. G'ORB cheated in the battle of the bands to make him win but at the end of the episode, T'ORB had become fed up with putting up with all of his plans, he stood up to him, overthrew him and let Grojband win. After this, T'ORB broke up the band, forced G'ORB to apologize, and made him give up evil and become good.
• Chloe Penn (character has no spoken dialogue) – A tall redhead girl who mainly appears in the show as a background character. Chloe is shown to have a romantic interest towards Nick Mallory, as well as Party Danimal in one occasion. Co-creator Todd Kauffman confirmed her to be Laney's older sister, albeit unofficially.^[14]