Continuity mistake: In the first scene where we see David Helfgott, there's a mark on his ring finger, probably made by a wedding ring. In that scene David isn't married.
Continuity mistake: Early on Nancy is in a limo and a man with long hair tells her to get drugs. While he's talking his hand goes from resting on his chin to resting on the armrest instantly.
Continuity mistake: At one point about three-quarters of the way through the movie, when Lowell Bergman (Al Pacino) and Don Hewitt (Philip Baker Hall) are talking, watch in the background as a certain lady walks past after Don says something. When we cut back to him he says something else, but the same woman in the background appears and walks exactly in the same direction, just like in the previous cut. (01:52:35)
Factual error: Warren Beatty refers to the "Hoover Dam" being able to generate the power needed for Las Vegas and his Flamingo casino. The problem is that he supposedly made the comment in 1937. At that time, the "Hoover Dam" was still called "Boulder Dam." It wasn't renamed to honour President Herbert Hoover until about ten years later.
Continuity mistake: When Yossi Ghinsberg falls from the plot to the river, he swims to left bank of the river (you can see the water flow from right to left). Afterwards he stayed on the same bank of the river. But later we see him to look down to the river from the right side (water flow is from left to the right). How did he get there? (00:52:25 - 01:14:23)
Continuity mistake: After Mick Mars has Nikki and Tommy kick the guy out with the guitar at his audition, the guy leaves and cries through the door. Nikki is standing by the door and looking nearly straight forward as the guy leaves, but then the camera changes angles and suddenly he's looking more to the side towards the door. Also his arms are a little higher up holding his guitar.