Carly Shay (Miranda Cosgrove) - 13 years old in the first season and 17 years old in the sixth and final season.
Sam Puckett (Jennette McCurdy) - 13 years old in the first season and 17 years old in the sixth and final season.
Freddie Benson (Nathan Kress) - 13 years old in the first season and 17 years old in the sixth and final season.
Spencer Shay (Jerry Trainor) - Carly's older brother and the guardian of the three main characters. His age is never explicitly stated in the show, but he is likely around 25 years old in the first season and 31 years old in the sixth and final season.
Other recurring characters include:
Gibby Gibson (Noah Munck) - A friend of Carly, Sam, and Freddie who often appears on their show. Gibby's age is never explicitly stated in the show, but he is likely around the same age as Carly, Sam, and Freddie.
Nevel Papperman (Reed Alexander) - A nerdy and unpopular classmate of Carly, Sam, and Freddie. Nevel's age is never explicitly stated in the show, but he is likely around the same age as Carly, Sam, and Freddie.