Seth Gesshel Green was born on February 8, 1974 to parents Herb Green and Barbara Gesshel in Overbrook Park, Philadelphia, Pennsylvania. Green's first well known role was that of Oz the werewolf in the television series Buffy the Vampire Slayer.

Green appeared in all three Austin Powers movies (as Dr Evil's son "Scott Evil") and in the short-lived television series Greg the Bunny, as well as voicing the character of Chris Griffin (among others) on the animated series Family Guy. He also starred in the series Four Kings, and guest starred on the comedy That 70's Show. He also appeared in the teenage sitcom Tucker, playing himself in the part of McKenna's boyfriend, and in one of the first episodes of The X-Files as a secondary character.

In 2005, Green co-created Robot Chicken with Matthew Senreich for Cartoon Network's Adult Swim and the Freshmen with Hugh Sterbakov. Green has also written for the magazine Toyfare and is a noted fan and collector of M.A.S.K. toys.