After losing his job, Randy Dupree (played by Owen Wilson) asks his best friend Carl Petersen (played by Matt Dillon) if he can stay with him and his new wife Molly (played by Kate Hudson) until he gets back on his feet. Carl hesitantly agrees, but Dupree's stay quickly becomes indefinite as he spends his days lounging around the house, watching television and disrupting the newlyweds' routines.
As time goes on, Carl becomes increasingly frustrated with Dupree's behavior, particularly when he starts to develop feelings for Molly. Meanwhile, Molly starts to see Dupree in a new light, appreciating his carefree attitude and emotional support.
To make matters worse, Carl's overbearing father-in-law (played by Michael Douglas) begins to meddle in their lives, putting pressure on Carl to kick Dupree out and causing tension between him and Molly.
Ultimately, Dupree must decide whether to continue his freewheeling lifestyle or take responsibility for his actions and make amends with his friends and their marriage.
The movie is a lighthearted comedy about friendship, marriage, and the challenges of growing up.