Other mistake: When young Vito Corleone shoots Fanucci in the chest at the doorway to his apartment, in a continuous shot, a wound/blood bursts from Fanucci's white vest. When Fanucci proceeds to tear his vest open seemingly in disbelief he has been shot, there is no entry-wound, blood or hole in his white shirt directly under where the wound appeared in his vest.
Continuity mistake: In the scene where Roth's symbolic birthday cake is divided among his partners, we see a shot in which Michael is seen, in long-shot, putting a forkful of cake into his mouth while talking about the rebels. The thing is, it does not sound as if he is talking through a mouthful of cake. What is more, when the scene cuts to closeup, he is not chewing anything, even though it's just seconds later.
Continuity mistake: In the Senate delegtion hearings, Michael made his speech saying he was awarded the Navy Cross. When you see Michael in uniform in Godfather I, he is wearing a Silver Star ribbon.
Factual error: In the scene of young Vito Corleone coming to America, his ship passes the Statue of Liberty going the wrong way, south, whereas the docks of Manhattan, where immigrants were dropped before being ferried to Ellis Island, are to the north.
Visible crew/equipment: In the scene where Vito shoots Fanucci, you can see the squib in Fanucci's waistcoat before it detonates.
Continuity mistake: Shortly after assassins try to kill Michael at his home, he meets privately with Tom Hagen. As Tom enters the room, the table is empty. Then, after they are talking for a few moments, Michael offers Tom a drink from a bottle of courvoisier that has magically appeared.
Visible crew/equipment: After the first scene showing the plane starting up it's engines and turning around, we are shown another scene of rioters throwing slot machines out of a club. In the bottom centre of the screen you can see a silhouette of what looks to be a part of a jigsaw puzzle piece on the camera. The object must be on the camera because when the camera pans to the right and down, the silhouette stays in the same position in the picture.
Factual error: When Michael arrives at Hyman Roth's house you can see the 1974 State of Florida green inspection sticker on Michael's car. The movie's supposed to be in the late 50's.
Factual error: At the New Year's party, when everybody is running out from the goverment's palace, you see the flags at the entrance are from Cuba, but the coat of arms is from Dominican Republic (the country where this scene was filmed).
Continuity mistake: Al Pacino is accused of killing the 5 family leaders in 1950. In "Godfather part I" the killing of the 5 family leaders took place in 1955.
Visible crew/equipment: In the flashback scene shortly after young Vito has killed Fanucci and then joins his family on the front steps, a boom microphone is visible above and to the right of the steps.
Continuity mistake: When Senator Geary talks to Michael in his Lake Tahoe office and the camera is on Michael there's an older couple (the woman is wearing a fur jacket) walking by outside. The camera cuts to Geary for a while, and when it cuts back to Michael the same couple is still walking by.
Plot hole: During Godfather I, when Michael was plotting the assassinations of the 5 family heads, he mentions to his father that his son Anthony is thee years old, and 'reading the funny papers.' In Godfather II, we begin at Anthony's first comunnion, and the date given is 1958. Yet, later at the party, Kay mentions to Michael that 7 years ago he promised the family would be completely legitimate. This was before they married and Anthony was born. (This promise was part of Michael's proposal to Kay.) 7 years ago would be 1951, so how could Anthony be 3 years old then?