Cleary first hit the pop market with the song "I.M. Me" while still using her given name. Her debut album, Everything I Wished For, was released independently under the Free Falls record label in 2002 after two years of recording. The album hit #45 on Billboard's Top Independent Albums chart. When Cleary signed with Jive Records in the summer of 2002, they asked to change her name because they already had a Britney on their roster. Her self-titled album, Nikki Cleary was released in the summer of 2003.
She was featured on a Nickelodeon Kids' Choice Awards record in 2003, with her single "1,2,3". She also performed on Nickelodeon's "All That." Cleary also did a version of "Summertime Guys", featured on the Kim Possible soundtrack. She contributed to the Mean Girls motion picture soundtrack with the song "Hated".