Although the family relocated many times, Munn was predominantly raised on Yokota Air Base near Tachikawa in Tokyo, Japan, and later moved to Los Angeles to pursue an acting career.
In 2004, Munn interned at Fox Sports Networks and worked as a sideline reporter for college football and women's basketball.
She has gone on to say that she disliked the experience, explaining "I was trying to be something I wasn't, and that made me really uncomfortable on live TV." Soon after she moved to Los Angeles, Munn was cast in a small role in the direct-to-video horror film Scarecrow Gone Wild.
She appeared in rock band Zebrahead's music video for their song "Hello Tomorrow" as the love interest of the lead singer Justin Mauriello. The network, devoted to the world of video games and the video game lifestyle, was at first hesitant to hire Munn.
In 2006, Munn moved on to the G4 network, where she began co-hosting Attack of the Show! Although she admits video games were her "weak point", she was confident in her technical knowledge.
On the show, Munn was featured with journalist Anna David in a segment called "In Your Pants", which deals with sex and relationship questions from viewers. , Munn hosted Formula D, a now defunct program about American drift racing, and an online podcast called Around the Net (formerly known as The Daily Nut), for G4. in December 2010 and was replaced by Candace Bailey.
She played the character Sloan Sabbith on the television series The Newsroom from 2012 to 2014 and appeared in the sequel film X-Men: Apocalypse (2016) as Psylocke. When Munn was two years old, her mother remarried to a member of the United States Air Force.
Munn appeared in ABC Family's Greek, portraying Cappie's love interest, Lana.
In May 2010, NBC announced that Munn would star on the television series Perfect Couples.
Munn had a significant role in the horror film Insanitarium in which she played a nurse at an insane asylum.
She had roles in the films Date Night (2010) and Iron Man 2 (2010). praised Munn for her improvisation skills and led the crew in a round of applause.The half-hour romantic comedy premiered on January 20, 2011.