Factual error: In the establishing shot of the movie producer's mansion, a car in the driveway is suppose to be a 1937 Cord, but actually it is a replica produced between 1968 and 1972. Real Cord cars had bug eye headlights that cranked out of the fenders. The replicas had fixed glass covered headlights in the fenders.
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)
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)QuantumGames