Continuity mistake: Michael shoots McCloskey in the throat with a black plated gun. The shot following shows Michael pointing a silver plated gun against a black background, so they probably needed something to stand out. Michael then finishes McCloskey with a black plated gun.
Continuity mistake: When Michael is sitting with Sollozzo and McCluskey, the owner (presumed owner) of the restaurant (shown from the rear, walks behind the bar to ring up and put a check in the register, he is smoking a pipe. (in his mouth) But yet a split-second later from a front angle there is no pipe in his mouth, hand, or anywhere near him.
Revealing mistake: When being transferred to another room the supposedly unconscious Don pulls his left arm up so it won't hit the door frame.
Suggested correction: He's shown to be awake when Michael is talking too him moments later, albeit weak. He was probably woken up by the movement before this point, so he was conscious enough to move his hand.
Other mistake: As the camera pans in on Woltz's mansion right before the horse's head scene, his bedroom is on the second floor. However, the windows in his bedroom show a courtyard in the background. The horse's head scene was filmed in a dining-room-turned-bedroom at a Guggenheim mansion on Long Island. The Guggenheim dining room is located on the first floor, as shown in a February 2022 episode of Antiques Roadshow.
Revealing mistake: When Tom is visiting with Waltz, it is a body double and not Robert Duvall walking outside on the way to see the horse.
Other mistake: When Michael arrives in Las Vegas at the Hotel Continental and exits the car two men are visible through the window inside the hotel who are dressed in 1972 contemporary attire, despite this scene being set in the 50s. The man on the left in a blue jacket looks as though he could be David Geffen. (02:19:38)
Visible crew/equipment: During the meeting between the Corleone family and Sollozzo to discuss drug dealing you can see a boom microphone reflected in the glass window when Don Corleone stands up to pour Sollozzo a drink, it can be seen moving around. A little later in the same scene when Don rejects Sollozzo's offer you can see a crew member reflected in the same set of window's moving around (above Sonny's head). (00:37:20 - 00:38:44)
Other mistake: While Michael is talking with the Sicilian father, requesting to meet his daughter, the camera jostles twice, between the close shots of both men. (01:40:00 - 01:46:00)
Continuity mistake: When Woltz shows Tom Hagen his horse, Khartoum in the stables, the horse has a prominent white star on his head. The horse's head in Woltz's bed later that night has no such star, the head is all black.
Continuity mistake: When Tom is walking down the alley between buildings at Woltz Studios before he meets Mr. Woltz, the bag he is carrying looks like a travel bag and is almost equilateral triangle shaped. When he meets Mr, Woltz, his bag is a much thinner (isosceles triangle) shaped briefcase. In almost every shot the hand carrying the "bag" is switched. (00:27:45)
Continuity mistake: When they leave to kill Pauli it's light outside, when they are driving and Clemenza says that they to get more mattresses it's dark outside, when they stop to kill Pauli it's light again.
Audio problem: When Vito Corleone is brought back from the hospital and he is upstairs in his bedroom with his other family members, after his grandson Frank gives him his gift, the baby who was just crying has his mouth completely closed while the audio has him still crying as they leave the room. (01:33:00)
