Factual error: All swords in this movie are made from steel, and in the beginning it's said that the film takes place years before the Pyramids were built (they were built around 3200 BC). Steel wouldn't be around for 2000 more years. (00:03:50 - 00:12:40)
Revealing mistake: When Mathayas is chasing the kid who stole his rupees, he crawls into a hole that's just big enough for him to fit through. But when Mathayas crawls in, the hole has grown - he should have only been able to fit on his stomach, but he goes through on his knees. (00:25:15)
Continuity mistake: When The Rock first enters the scientist's room, the scientist explains to the child about his magic powder. This is on a device that's slowly turning and sifting off a little of the powder at a time, yet during one cut away and back, a lot more powder seems to have disappeared off the mechanism than it would have pushed off itself. (00:27:00)
Other mistake: When the guards are breaking into Cassandra's bathing room, we see a guard's arm reach through a hole in the door to unlatch it. However, you can see the door has come off the jamb, with a big gap, before he reaches down to pull the latch.
Continuity mistake: In the scene where Cassandra and Mathayus get out of the well after falling through the tub. When they are showing Mathayus from the back of his head his hair looks wet all over but when they show his face, the hair on his head looks dry while the long parts of the hair is still wet. His face has also been dried off when last seen. (00:34:10)
Factual error: During Memnon's training session, at least one of his opponents uses a Japanese training sword known as a shinai. You can see this most clearly after the fight, when one of the weapons lying on the ground comes into view. Not only did the Egyptians and Japanese not have any contact with each other at this time, but this particular training weapon had not yet been invented.
Audio problem: When Mathayus and his friends are attacking Memnon's palace, there is a scene where Memnon's general rides at Balthazar on a horse, but then falls off. Balthazar holds a spear at his neck. The shot then changes so we can't see the general and he stabs him and he screams loudly. But if the spear went through his neck (as it should have, as it didn't move anywhere but down) he should not have been able to scream. (01:16:55)
Factual error: The scientist claims that he is working on a magic powder (gunpowder) that was devised by the Chinese. Firstly, the Egyptians had no knowledge of the Chinese in those times and secondly, the Chinese didn't invent the gunpowder for at least another 4,000 years. (00:27:00)
Continuity mistake: When Balthazar knocks Matathyus down, Matathyus falls face down and his hair gets covered with white bits of dust (sand or whatever). A brief second later, when he stands up, his hair is clean and shinny, but he hasn't had time to clean it, or even made a single move to take the dust away.
Other mistake: In the rebel village toward the end of the movie, Balthzar's scar on the left side of his face keeps changing. Sometimes the scar is barely there and others it is only partially there. (01:13:40)