Revealing mistake: In the scene where Romeo and Roy snap all the clubs other than the 7-iron, Roy drops his golf ball onto the grass. However, when he hits the ball, a white tee can be seen travelling up towards the top left of the screen. The tee can easily be seen but is much clearer in slow motion.
Continuity mistake: When Molly comes for her first golf lesson, Costner takes the last bite of his hot dog. In the next scene, he still has some of the hotdog left.
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.