Revealing mistake: In the scene where Lorraine Bracco points a revolver at Ray Liotta's head, after Ray Liotta turns the tables and now points the gun at Lorraine Bracco as he gets up and walks away you can see Ray Liotta steps on Lorraine Bracco's hand and she opens her mouth wide like shes screaming but it must have been cut from the audio, as Ray walks off camera his expression changes to show that he knew he had accidentally stepped on his co-workers hand.
Revealing mistake: In the scene where Karen is too afraid to accept free clothes from Jimmy and speeds off, the yellow NY state license plate falls from the parked car to reveal the modern white one underneath.
Factual error: In one scene we are introduced to Idlewild Airport in 1963. We're shown a couple of aircraft in flight and one of the aircraft is a Boeing 747 in the livery of KLM Royal Dutch Airlines. The Boeing 747 didn't enter commercial service until 1969.
Continuity mistake: It's the scene where Henry and Karen are visiting some friends and they have their children with them. Henry starts to greet his friends, he is then carrying a big brown teddybear in his hand. Then Paul starts talking to him about Billy for a while, when the camera then is behind them as they walk away Henry is holding a little pink teddybear and he had no opportunity to switch.
Continuity mistake: In the scene that Karen is too afraid to take the clothes and the license plate falls off, there is a shot of the windshield which is close enough to reveal the fake registration sticker made for the era in which the movie was represented. The problem is though that not only is it obvious that the sticker is applied on the outside of the window, but the current sticker (inside the window) is larger than the movie prop and can be seen as a "frame" around the other.
Continuity mistake: When Tommy is having a go at Henry in the Copana bar about saying he's a funny guy, the shots from behind Tommy, Henry has his left elbow leaning on the table with a cigarette in his hand. In the reverse shots(behind Henry) his arm is down. This continues throughout the "How am I funny" speech.
Continuity mistake: The scene in the restaurant where Joe Pesci messes with Ray Liotta saying, "What, am I funny, am I a funny guy to you?" watch the drinking glasses on the table. The drink levels are going up and down with and then without ice.
Continuity mistake: When Henry Hill is in jail and talking with his wife, the child is playing with a stack of coloured toy blocks. The order the blocks are stacked in change in different shots.
Continuity mistake: When Tommy shoots Spider in the foot and he goes down, Henry is playing cards at the table, then in the next scene Henry is helping Spider up, then the very next scene Henry is back at the table watching Spider crawl on the floor.
Continuity mistake: In the scene at Idlewild airport, the actors walk past the rear of an easily identified 1965 Chevy Impala. Occasionally Chevrolet introduced vehicles early, but never two years early.
Continuity mistake: In the scene after the 'robbery' of the suitcase of cash by Henry and Tommy, Pauly, Jimmy, Henry and Tommy are all celebrating their success, laughing etc. with the suitcase of cash on a table. While Pauly is telling Henry to tell anyone who asks that he won the money playing craps in Vegas, Jimmy is standing quite some distance to the left of Henry.When the camera closes in on Henry and Pauly, Jimmy has moved positions - he is now directly behind Henry's right shoulder (on the left of shot). This is obviously for effect so Jimmy can be seen laughing in the background.
Continuity mistake: When Jimmy and Henry are talking to Morrie and the camera angle is behind Morrie you can see him holding the phone at his shoulder, when the camera angle switches he has the phone at his ear. Then the phone suddenly disappears when you can see both of his hands and then it comes back again right before Jimmy strangles him with it.
Continuity mistake: In the scene where Pauly talks to Henry and the restaurant owner about Henry's possible involvement in the restaurant biz, Pauly is talking (with the cigar clearly in his hand and it cuts away to him saying "No?" with the cigar jammed directly in his mouth.
Factual error: Early in the film, when Henry Hill is selling Pall Mall cigarettes out of a car trunk and is arrested, there are UPC price codes visible on the cartons of cigarettes. UPC codes were not used on products in the 1950's when the scene is taking place. They were introduced in the mid 1970s.
Continuity mistake: Whilst Jimmy is choking Morrie in the wig store the phone suddenly rings and the shot changes. Between shots the way Morrie is standing has all of a sudden changed. Instead of leaning back, he is bent forward. The way he is holding the phone whilst being choked changes as well.
Continuity mistake: When Henry is in prison, Karen comes to visit him and drop off goods she smuggled in. They begin to argue while Henry is holding his daughter and Karen starts placing all the goods on the table. The camera angle switches to just a view of Henry's hands gathering the goods and if you look carefully, you will notice that BOTH of Henry's hands are collecting the goods. This would be impossible considering he is holding his daughter in one of his arms. Once the goods are collected, Henry is seen holding his daughter again.