Plot hole: In the scene where Roy takes his ball out of the hole, at the last round of the US Open, the crowd are going wild etc. Dave, who has a chance to win the competition, doesn't finish off his round.
Continuity mistake: During the press conference at the U.S. Open where Roy begins to list the companies who are sponsoring him, he says that one of them is "Woody's Smokehouse" when the patch on his jacket says "Wally's Smokehouse".
Romeo Posar: Now THAT was a defining moment. And the definition was "shit."
Trivia: Kevin Costner made most of his own golf shots in this film.