Barnett was born in 1983 in Clinton, Maryland, a suburb of Washington, D.C. Having pursued acting since 2000,[1] and with an interest in promoting social change, he moved to Los Angeles by 2005.
In the early 2000s, in Los Angeles, Barnett landed a role in a play about homeless youth called The Playground.
Barnett's films also include a 2013 short called The Newest Testament (a Biblical parody which he produced, co-wrote, and stars in as Jesus), The Scribbler (2014), and The Treehouse (2015).
In his first major project for Funny or Die, Barnett starred in, co-wrote, and co-produced Growing Up With Gosling (2012), in which Barnett plays the childhood best friend of actor Ryan Gosling, who has tried to cast him as his co-star in all of his movies, including The Notebook, Ides of March, Crazy, Stupid, Love, Lars and the Real Girl, and Drive.
[15] Barnett next starred in, co-wrote, and co-produced Kickstarter to help Luke & Tanner do COOL STUFF!, which premiered in April 2013.
[16][17] In reviewing the spoof, Mashable noted that "... Hollywood stars have recently come under fire for using Kickstarter because, as the argument goes, they may deflect attention from lesser-known filmmakers who rely solely on crowdfunding to support their projects.