Continuity mistake: Towards the beginning of the movie, young Alexander is receiving a wrestling lesson and his hair is extremely blonde. A short time later, young Alexander is outside with his teacher and fellow students and his hair is more brownish-blonde. (00:05:45)
Continuity mistake: In the scene were Queen Olympias is walking towards Alexander with a snake around her arm, there is a two second clip at Alexander and then Olympias is seen again but not holding the snake anymore. (00:09:30)
Revealing mistake: Towards the beginning of the movie, young Alexander tames a horse and then jumps on the horse and rides off. He is supposed to be riding bareback, but in one of the shots from a distance, you can tell that the actor's feet are in stirrups.
Factual error: The backdrop to the party scene in India shows a large building with glass windows. The Romans were the first to use glass windows some 300 years later.
Deliberate mistake: When Alexander is giving his pre-battle speech at Gaugamela, some of the shots are 'flipped', which has the odd effect of suddenly making all of the phalanx pikemen left-handed.
Factual error: Just before old Ptolemy starts telling his story of Alexander, at the very beginning of the movie, we see a shot of the famous Lighthouse of Alexandria. It's fully operational, which is a mistake because the building was finished during the reign of Ptolemy's son, Ptolemy II Philadelphos, some years after the first Ptolemy's death.
Continuity mistake: When Alexander builds an altar for Titans to mark the furthest point he has reached, both him and Hephaestion are reasonably recovered from severe wounds they suffered during the battle of Hydaspes, which was the last battle mentioned. However, we can see scratches and minor injuries on many characters' faces that appear very fresh and would have disappeared without a trace in the time it took for the deeper wounds to heal.
Factual error: Contrary to what's depicted in the movie, Cleitus was never involved in the murder of Parmenion. He was in fact on his way to Alexander when Parmenion was killed.
Continuity mistake: During the battle of Gaugamela when Macedonian and Persian cavalry are riding in parallel (with Macedonian infantry hiding behind the cavalry) Alexander gives an order for the cavalry to turn left and the infantry to go forward. In detailed shots from the ground we can see the horses slowing down and turning. But in the wide shot from above we can see the infantry turning left instead to emerge from between the horses and the cavalry continue to ride straight in the original direction.
Revealing mistake: In the scene where Alexander sees the dead king Darius and puts his cloak on him, if you look closer, you can see that the character is breathing. Look closely at his belly.
Other mistake: In the battle at Gaugamela scene where Cleitus jumps off his horse to help Alexander in the battle, Cleitus is seen cutting the head off a barbarian and throwing it at another. Two seconds later he is seen swinging that same head back and forth.
Revealing mistake: When Alexander rides towards the elephant of the Indian King, his sword is obviously waggling and his helmet is bouncing out of shape as though made of rubber.
Continuity mistake: The scar on Old Ptolemy's forehead switches sides halfway through his first scene.
Factual error: The event of wounding Alexander by an arrow that punctured his lung is depicted with great attention to detail and shown exactly as described by historians. However, in reality, it happened during the storming of the Mallian Stronghold, not during the battle of Hydaspes.
