Character mistake: The sign for the hotel where Jake is staying at in Mexico says Tengo Quarto's para Renta. The word is spelled wrong. It should say CUARTOS. Also, there is no apostrophe s in cuartos. It is plural, not possessive.
Factual error: Joe Jackson batted left-handed in real life, not right-handed as Ray Liotta portrayed. He also threw right-handed and not left-handed like it shows when Kevin Costner is hitting him fly balls to left field.
Other mistake: When Miyagi throws Mike into the light switches, the lights go out but the switches never change position.
Revealing mistake: When Kurt is loading his brother into the van on the stretcher after the fight when he has just been paralyzed his feet are sticking out, but when the door is being shut he pulls them in.