Walter Mitty, played by Ben Stiller, works in the photo department of Life magazine, but his life is arguably uneventful. He often daydreams about incredible adventures and frequently zones out at work due to his vivid fantasy life. Despite his lackluster existence, Walter harbors a secret admiration for a colleague named Cheryl, played by Kristen Wiig, and longs to ask her out.
However, when Walter's job is threatened due to the magazine's transition to online publishing, he sets out on a real-life adventure to locate a missing negative that is to be the final cover image for Life's print edition. The negative was sent to noted photographer Sean O'Connell, played by Sean Penn, and Walter must track him down to retrieve the image.
Walter's journey takes him from his mundane life in New York City to Iceland, where he has a series of hilarious mishaps and stunning encounters with nature. Along the way, he confronts his fears and takes risks that he never would have dreamed of before.
As Walter's adventure unfolds, he finds himself experiencing moments of genuine excitement and discovery, and ultimately discovering the true meaning of life. Along the way, he also catches the eye of Cheryl and comes to realize that the life he's always dreamed of may not be so out of reach after all.