DeSena is best known for his work on the sketch comedy series All That, having joined the show's cast at the start of its seventh season in 2001. His family moved to Irvine, California, in 1999 where he attended school. He was an active member of the international ComedySportz troupe, a comic improvisation team that participates in games as seen on Whose Line is it Anyway?.
In 2007, he appeared in one episode of King of the Hill and wrote and starred in the mockumentary web series Dorm Life, which won a 2008 Webby Honoree for Best Writing and Comedy: Individual Short or Episode. He appeared in one episode of Generator Rex, and in 2012, he starred in the Hulu original series Battleground. He has appeared as two separate characters in the Nickelodeon series Sam & Cat, and in 2014, he voiced Robin in the animated film JLA Adventures: Trapped in Time. In 2018, he voiced Callum in the animated series The Dragon Prince, working with former Avatar alumni Aaron Ehasz and Giancarlo Volpe.
2005: Won a Young Artist Award for All That (Best Performance in a TV Series (Comedy or Drama) - Leading Young Actor) (shared with Logan Lerman)
It is stated in a Nickelodeon Magazine Presents: Avatar issue that the creators originally intended Sokka to be much more low-key, but when DeSena came in and brought liveliness to his character, they began to give him more ad libbed and humorous parts.
During the recording of Book Two, Jack was studying in college and as a result, was frequently late for recording sessions. DeSena would later admit he had behaved like "an unprofessional 18-year old."
DeSena was once cast as DC superhero Robin, a role which was also auditioned by his fellow Avatar co-star Dante Basco, in the film JLA Adventures: Trapped in Time.