Deuce Bigalow ( Rob Schnieder) is a diminutive, sex-starved fishtank repairman and fish caretaker. Deuce has no success in attracting women, so he tries to stay busy with work. On a house call, he meets male prostitute Antoine Laconte (Oded Fehr). Antoine is going on a business trip, and he asks Deuce to care for his lionfish and home while he's away. Deuce accidentally sets Antoine's kitchen on fire when trying to make a grilled cheese sandwich in the toaster, and smashes an expensive fish tank.
Fearing for his life, Deuce is forced to find a way to pay off Antoine for the damage. Low-rent pimp T.J. Hicks (Eddie Griffin) offers to help Deuce make enough money to buy a new fish tank, and convinces Deuce to take over the absent Antoine's role as a gigolo. Deuce meets unusual clients; they include a woman who's narcoleptic, one suffering from Tourette's Syndrome with coprolalia, another who weighs close to 750 pounds, and an extremely tall woman. Deuce decides to make the clients feel better about themselves, since he only desires to have sex with beautiful, sexy women.
Deuce is pursued by Detective Chuck Fowler (William Forsythe), who demands Antoine's black book of clients and threatens to take Deuce to jail if he doesn't comply. Deuce falls in love with one of his clients -- Kate (Arija Bareikis), who has a fake leg. She breaks up with Deuce when she finds out that he was a prostitute hired by her friends.
Deuce helps Detective Fowler please his wife via stripping and erotic dancing, and the two make peace. Deuce is still taken into custody on prostitution charges, as Fowler needs someone to bring in. At the hearing, it is revealed that Deuce never slept with any of the clients except for Kate. Since Deuce gave back the money to Kate and was not paid for sex with her, he is cleared of all charges.
Using the money he made, Deuce restores Antoine's fish tank. Unfortunately, one of Deuce's friends accidentally kills the prize fish in Antoine's aquarium. Deuce buys a replacement fish and returns to Antoine's house just in time. Antoine is suspicious, but cannot figure out why. He taps the new aquarium and the glass shatters. Deuce then reveals his man-whoring escapades to the confused and angry Antoine. Outraged, Antoine tries to kill Deuce, but the overweight client shows up, comes between the two men, and saves Deuce's life. Antoine is then arrested by Detective Fowler. Deuce marries Kate.