Schwartzman's acting career began when he was 17 years old when he starred in Wes Anderson's Rushmore in 1998. Prior to Rushmore, Schwartzman had no acting experience. Shortly after in 2000 Jason had a guest role in the short-lived series Freaks and Geeks.
He made a cameo appearance in the Judd Apatow-produced musician biopic spoof Walk Hard as Ringo Starr. In 2009, he appeared in Apatow's third directorial feature entitled Funny People, in which he played Mark, a C-list television star.
In 2007, he created the indie rock solo act Coconut Records. The first CD, entitled "Nighttiming" was produced by Mike Einziger of Incubus and features a cover photo from Roman Coppola. The album was first released on iTunes on March 20, 2007. Songs include "West Coast", "Nighttiming", and "This Old Machine". In 2009, the second album Davy was released on iTunes on January 20, 2009. The first single from the CD was "Microphone".
Schwartzman married long-time girlfriend Brady Cunningham at their home in the San Fernando Valley on July 11, 2009. Cunningham is Art & Design Director and co-owner of TENOVERSIX based in Los Angeles. Schwartzman is a vegetarian and describes himself as "basically" a vegan due to not eating meat, dairy or eggs. Schwartzman narrated a video, What to Eat: The Environmental Impacts of our Food, for Farm Sanctuary. He has two daughters, Marlowe Rivers Schwartzman, born on December 4, 2010 and another born in May 2014