According to Entertainment Weekly, the Attack of the Show! host will play a glamorous spy who encounters secret agent Chuck (Zachary Levi).
The character reportedly "intimidates and schools" Chuck and his friend Morgan (Joshua Gomez).
It was previously announced that Rocky IV star Dolph Lundgren will play a villain in the episode.
Munn has also been cast as a series regular in NBC's forthcoming romantic comedy Perfect Couples.
The Chuck season premiere will air on September 10 on NBC.