Sherman 'Tank' Turner (Dane Cook) is a help line operator with a hobby. If a guy loses a girl and wants her back, he gets in touch with Tank and pays him to take the girl on a bad date. Throughout the evening Tank inevitably behaves in the most moronic fashion causing the girl to realize that her ex was not really such a bad guy after all.

He shares an apartment with his step cousin Dustin (Jason Biggs) who has fallen for his work colleague Alexis (Kate Hudson). Dustin takes Alexis on a date and confesses his love but she insists they remain friends. After the date Dustin explains his situation to Tank who volunteers his services. Dustin initially turns him down but the next day sees Alexis flirting with another co-worker and begs Tank to take Alexis out.

Tank bumps into Alexis and they arrange to go out. He behaves badly all night but Alexis is too drunk to care. When he drops her off she expects him to come in but he resists the temptation out of loyalty to Dustin. Alexis calls Dustin but when they meet she explains that her date with Tank has motivated her to see other men. Dustin sends Alexis roses and an apology poem in Tank's name. Alexis calls Tank at work and berates him for leaving early the previous night.

Tank goes to see Alexis and they end up having casual sex on a regular basis while Dustin begins a series of desperate attempts to stay friends with her. Tank's feelings for Alexis start to grow but after consulting with his father (Alec Baldwin), he has doubts that he is deserving of a serious relationship with her. While attending the wedding of Alexis' sister Rachel (Diora Baird), he realizes that she is one of his previous bad dates. The groom, Josh (Taran Killam), asks Tank to keep quiet about his use of his services. After overhearing Alexis telling Rachel that she has fallen for him, Tank's guilt causes him to sabotage their relationship and call Dustin to apologize.

Dustin arrives at the wedding reception and reveals Tank's schemes to Alexis. Tank points out his clients, including the groom, and is punched and thrown out. Alexis, distraught from the fact that she felt used, never wants to see either of them again. Later, while talking with Dustin and his father, Tank realizes that he loves Alexis and they encourage him to reconcile with her. He finds her and jogs with her for a few miles, in the attempt to make amends, but Alexis is unmoved.

Three months later, Tank is on a date when Alexis and her roommate Ami (Lizzy Caplan) see him. Alexis walks up to him and throws wine in his face, ruining his date. She then lets it slip that both she and Rachel are pregnant with his children. Tank, who is shocked but also happy, engages in a play argument with her. After some name-calling and bantering, they kiss and reconcile.