Continuity mistake: When Stanley Ipkiss first appears as the Mask, after having jumped through the end of hall apartment window with Mrs. Peenman shooting at him, he is approached by several thugs, one of which asks him the time. The thugs begin chasing him down the alley. The thug with the beard and baseball cap at the beginning of this chase is shirtless. Halfway through the chase he now has a flannel shirt on which is unbuttoned, (visible when he jumps over a barrel as it flies open). As he stops, now the flannel shirt is buttoned up to the very top button. The entire chase scene is 4-5 seconds long. (00:19:45)
Continuity mistake: When Stanley is trying to get in the club, Dorian tells the bouncer to "lose him". The line is immediately repeated due to an editing screw up. (00:10:51)
Continuity mistake: In the very beginning, when the scuba diver is trying to open the chest and gets hit with the pipe, at first the pipe is held by a rope near the middle and when it's lowered into the water it is held by a chain at each end. After it hits the guy and is let go from the chains they are wrapped around three times. (00:01:00)
Continuity mistake: The "loaner" car Stanley picks up at the mechanics is a 1951 Studebaker Champion. However, the car that falls apart on the bridge is a 1950 Studebaker Commander.
Continuity mistake: When Dorian puts on the mask for the first time, right before all the smoke starts reducing, pay close attention to his goons. Some of them change position. (Clearly those were two takes pasted together, one with Dorian without the mask, and one with.) (01:04:25)
Continuity mistake: When The Mask first visits the Coco Bongo and dances wildly with Tina, they perform a series of impressive manouvers and The Mask then dips Tina and holds her in that position. At this moment, Tina is revealed to be a stunt double, not Cameron Diaz, just before the camera zooms into a close up of Jim Carrey.
Revealing mistake: When Ipkiss is in jail and he is summoning Milo, the dog jumps up through the bars. When Ipkiss pulls him through, one of the bars swings a little bit. It must not have been a very secure cell. (01:13:00)
Continuity mistake: When Dorian's boss shoots him in the stomach it switches from the boss to Dorian several times. Each time Dorian's buttons change colours from black buttons to white buttons to no buttons. (01:18:25)
Continuity mistake: When Tina goes to the jail and meet Stanley they almost kiss for the first time. She is wearing bright red lipstick. A few minutes later she is running down an alley outside of the prison from Dorian. She is wearing soft pink lipstick. (01:09:00)
Continuity mistake: While in Mrs. Peenmans' hall, just before she shoots him, his hands switch places on the mallet. In the first shot, his left hand is on the bottom, right hand is on the top. In the other two shots, it is vice-versa. (00:18:15)