The banker Carl Allen(Jim Carrey) is a lonely man with low self-esteem after his divorce with Stephanie(Molly Sims), for whom he still yearns. He avoids his best friend Peter(Bradley Cooper). He has a boring job, stalled in a bureaucratic position in the loan department of a bank; and he spends his spare time watching DVDs. When he meets by chance his former high school mate Nick(John Michael Higgins), he is convinced to participate of a self-help program called "Yes Man" leaded by the guru Terrence Bundley(Terence Stamp). The basic principle of the program is to say "yes" to new situations, leaving the negativism aside. Carl misunderstands the concept and says "yes" to every question. While leaving the encounter, he helps a homeless man and in the end of the night he meets the gorgeous Allison(Zooey Deschanel) that helps him with her scooter. His life completely changes with his new attitude.