Audio problem: When Henry asks Karen who assaulted her, she says "this guy who lives across the street from me that I've known all my life", but when she turns to face toward the camera her lips moving don't match what she's saying.
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.
Factual error: 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.
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. (02:11:35)
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. Additionally, one of the 747s shown is actually a 747 'SP' (for 'Specual Performance') a version of the Jumbo Jet with a shorter fuselage which did not enter service until the mid 1970s.
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. (02:11:30)
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. (00:37:40)
Continuity mistake: When Pauly talks to Henry and the restaurant owner about Henry's possible involvement in the restaurant biz, Pauly is talking with the cigar in his mouth and it cuts away to him saying "No?" with the cigar in his hand. (00:25:55)
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: 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. (01:09:30)
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. (00:13:20)
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: When Paulie and Jimmy go to visit Henry at Janice's apartment to talk to him, after Paulie sits down and begins the conversation, a Star of David necklace can be seen around Henry's neck. The next time the camera is on him, it has switched to a crucifix and remains that way.
Factual error: In the scene where Henry pistol-whips Karen's neighbor, Henry is driving a 1966 Chrysler, when it 1964 at the latest. We know this because at the end of the movie it says that Henry and Karen were divorced in 1989 after 25 years of marriage. That means they were married in 1964.
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 Henry is in prison and he comes in to the kitchen with food in a bag, he first passes some bread to Paul. In one shot he picks up 2 jars and a bottle of wine. The next shot he is carrying the same food but suddenly has a loaf of bread in his hands. When the camera angle switches we now see Henry in front of the table about to sit at the table but now has no food in his arms. (01:22:10)