Continuity mistake: When Priam, Paris, Glaucus, et al, arrive at the beach to see the Greek's 'Trojan' horse, the men who lie dead all over the sand change position. Particularly, in the first shot as it pans towards the horse, the two dead men in red lie on the sand in front of Priam a good distance away from the horse. In the next two close-ups of these men (the same two bodies), their positions are completely different. Then in the next wide shot, those two bodies are much closer to the huge 'Trojan' horse now.
Continuity mistake: The cuts on Hector's face change and the one over Hector's left eyebrow actually changes direction, as well as other characteristics in many shots. When he shows his wife the tunnel, the top of the cut points towards the left side of his face, but when he stands at the gate and glances back at Helen, the top of the cut points up towards his right.
Continuity mistake: After Menelaus dies, during the Greek charge Hector spots Ajax doing his thing and the rolled white tourniquet around Ajax's leg wounds is clearly visible. When Hector rides toward Ajax, he promptly knocks Hector off his horse and the tourniquet is once again visible, only now it's wider and tied differently, and changes again within the following shots.
Continuity mistake: As Helen says, "They're coming for me. The wind is bringing them closer..." she leans on the large pillar, even as Paris walks over she stands beside it when they embrace. In the following wide shot, as Paris lets go of her, they are not standing in the same location as the previous close-ups.
Continuity mistake: When Menelaus bursts into Helen's room, as he confronts the handmaiden about her whereabouts, Menelaus' hair curl is in front of his shoulder when the shot faces the woman, but not when the shot faces Menelaus. The same thing happens with Paris when he is with Helen, with Glaucus when he says goodbye to Hector, when Hector speaks with Lysander at the armory and so forth. Throughout the film all the men's hair in front and back - its position, neat or not, curls or not, etc., noticeably changes between shots.
Visible crew/equipment: In the shot of Hector as he lies dying, there are shadows on his chest plate that are not his own, nor do they belong to Achilles - must be the camera.
Continuity mistake: When Paris and Menelaus face each other and then begin to fight, the shadows keep changing, and when the camera angles show each man's perspective, each man has his shadow to his own right hand side, even though they are opposite each other.
Factual error: Probably the most common mistake in all the ancient warfare movies like Troy. The thick leather armour that soldiers wear is almost impossible to pierce with such crudely sharpened swords but they always seem to pierce the armour with effortless ease.
Continuity mistake: At the start of the first battle when we see Achilles' soldiers penetrate the sands of Troy, Achilles throws a spear through a guys head. But if you look closely at the previous shot, the soldier's body is side-on, obviously so he can shoot the arrow, yet when it cuts to the spear going through the head, the soldier is completely facing Achilles.
Continuity mistake: When Briseis runs to Paris and shouts, "Paris! Don't!" in the wide shot, Achilles limps near the dead soldier on the grass. When Achilles is hit with the final arrow he drops to his knees and behind him an arrow lies on the ground (it is the 2nd arrow that hit him, which he pulled out and threw), opposite the dead soldier, which was much farther back in the previous wideshot of the grass.
Continuity mistake: After Agamemnon's death, Achilles kills the two soldiers to rescue Briseis and in the close-up as he starts to lift her, the soldier's helmet lies near his head by the steps and the sword's grip at his fingertips. In the following shots the body, sword and helmet all change positions, the helmet moves at least a foot and the sword moves a few feet.
Revealing mistake: Throughout the movie, especially in the scenes which take place in the Troy encampment, no matter how many times Achilles gets dirty in battle and then cleans up, there is always a small smudge on his left upper arm. In the right light, you can make out the distinctive, small, circular scar of a small pox vaccination right where that dirt smudge is - it's really quite distracting. Until 1972 in the US this was a common vaccination given to children.
Continuity mistake: Hector's sword slice,s Achilles's armor but the one shot shows the hit much higher up near the right shoulder than when we see a close up view and the cut is down by his ribs.
Continuity mistake: While still in Sparta, when Helen stands up after Paris rubs her neck, the strap of her dress on her right shoulder is closer to her neck when she removes the dress, than in the previous shot.