Zak Penn's career began as a screenwriter when he sold his first script, Last Action Hero, at the age of twenty-three. Since then, Penn has become known for his work on numerous films based on Marvel comics, including X-Men 2 and X-Men: The Last Stand, The Incredible Hulk, and The Avengers. He has also dabbled in other genres, writing scripts for disparate films such as P.C.U., Behind Enemy Lines and Suspect Zero.

Penn's shift into independent cinema began when he collaborated with his idol, Werner Herzog, on the script for Rescue Dawn. Penn directed and co-starred with Herzog in Incident at Loch Ness, his award-winning "hoax" documentary about the legendary director's attempts to make a film about the equally legendary monster. The Grand, Penn's second completely improvised film, was his third film with Herzog, and featured an eclectic cast including Woody Harrelson, David Cross, Ray Romano, Cheryl Hines, Dennis Farina and Gabe Kaplan.

In addition, Penn co-wrote the original story for Antz and produced the animated film Osmosis Jones. His first foray into television was the critically acclaimed SyFy Channel original series "Alphas" starring David Strathairn. His most recent endeavor was video game documentary Atari: Game Over, which recently premiered on Xbox Live.