Born in Los Angeles on May 14, 1993, she began her acting career at a young age, appearing in several commercials as well as the pilot episode of Smallville. Her breakthrough role came in 2002, when she played the role of Summer Hathaway in the film School of Rock, a comedy hit starring Jack Black. In the wake of School of Rock's success, she was cast in a supporting role on the children's television sitcom Drake & Josh (as Drake and Josh's kid sister, Megan Parker.

As Drake & Josh drew to a close, Cosgrove landed the lead role in iCarly, another popular Nickelodeon sitcom. Cosgrove also performed the show's theme song, which was commercially released in 2007 and became a hit soon after, driven in large part by YouTube views and downloads. iCarly: Music from and Inspired by the Hit TV Show appeared one year later, featuring four performances by Cosgrove and additional music by the likes of Sean Kingston, Menudo, and the Naked Brothers Band. By the end of that year, Cosgrove had also released a holiday single, “Christmas Wrapping” (a cover version of the Waitresses track), and started to work on a full-length album. Her song "Raining Sunshine" landed on the soundtrack to Cloudy with a Chance of Meatballs in 2009, and she released her debut album, Sparks Fly, one year later. ~ Jason Birchmeier & Andrew Leahey