Luke Hemmings as Drake Parker: Becca's biological brother, Calum's stepbrother, Jesy's biological son, Michael's stepson.
Calum Hood as Josh Nichols: Becca and Luke's stepbrother, Jesy's stepson, Michael's biological son.
Jesy Nelson as Audrey Parker-Nichols, Calum's stepmom, Luke and Becca's mother.
Michael Clifford as Walker Nichols: Calum's biological father, Luke and Becca's stepfather.
(portrayed by Lucy Hale) as Megan Parker: Luke's biological sister, Calum's stepsister, Jesy's biological daughter, Michael's stepdaughter.
Shawn Mendes as Craig Ramirez, Calum's friend.
Harry Styles as Eric Blonowitz, Calum's other friend.
Perrie Edwards as Mindy Crenshaw, Calum's girlfriend and an ex-science fair rival.
Jade Thirlwall as Helen Dubois, manager of the Premiere movie theater.
Ashton Irwin as "Crazy" Steve, employee at the Premiere.
Louis Tomlinson as Gavin Mitchell, another employee at the Premiere.
Ally Brooke Hernandez as Mrs. Hayfer, Luke and Calum's teacher at Bellview High School.
Normani Kordei Hamilton as Jackie
Niall Horan as Dr. Glazer, a doctor who lives across the street from Luke and Calum, who usually charges them a lot despite not doing much.
Selena Gomez as Leah, an employee at the Premiere who appears in season 4.
Niall Horan as Wade Shay
Taylor Swift as Addie Singer
Zayn Malik as Scottie
Dove Cameron as Rina
Nick Jonas as Paul