During Hector and Achilles' battle, Hector swipes his sword at Achilles's chest, leaving a big scratch on his armor. When Achilles kills Hector, his armor has no marks.
While Paris fights Menelaus for Helen's hand, their shadows are opposite, which means the sunlight was on both of their lefts as they faced each other. They do not match up; the scenes must have been shot at different times of the day.
When Hector lifts the helmet off the dying Patroclus, Patroclus' nose is bleeding. Five seconds later, when Patroclus is dead, he shows no sign of a nosebleed.
When Paris first shoots Achilles, half of the arrow goes clear through his heel. Later, when Achilles is dying, the entire arrow protrudes out of one side of his heel.
As Patroclus enters Achilles' tent to ask if he will join the Greeks to fight the Trojans, Achilles is seated while eating and drinking. In disgust at Patroclus, Achilles dashes the contents of his cup on the fire. Moments later, he drinks from the empty cup.
The Trojan War was a 10-year siege, but according to the movie, it's over relatively quickly.
Achilles drives Hector's body straight away from the battlefield. In the Iliad he drags Hector's body right round the walls of Troy.
Achilles' ship was not the first to reach the Trojan shores, but Protesilaos'.
The name of the King of Sparta is pronounced 'Men-uh-LAY-us', not 'Men-uh-LOUSE'.
Achilles kills Hector with a spear. When Achilles drags Hector back to camp, the spear sticks out of him. In the next shot, when Achilles is back at camp, the spear in Hector is gone. Hector was dragged for many miles, so it's very likely that the spear either snapped off or fell out by the time he reached camp.
Achilles throws his sword at a Trojan; it lodges into his opponent's head. Afterward, he uses a sword to behead the golden statue. Just before Achilles threw the sword into the Trojan's head, he had one sword in each hand, and he only threw one.
When Paris fights Menelaus, the view from Paris' eyes makes it appear that Paris' helmet has no nose protection. Paris' nose protection, a slim piece of metal placed directly between the eyes, would not be visible by the wearer.
When the Greek soldiers collect wood for the Trojan horse, bits come off the wood, revealing the white Styrofoam underneath.
When the Greeks first charge Troy, soldiers run toward the city walls carrying spears. Some soldiers' spear tips are wiggling, indicating soft rubber props.
When Achilles introduces Patroclus to Odysseus, his wooden training sword is in the foreground. The tip and edges are worn, revealing that the sword is painted plastic.
Just before Achilles says "You gave me peace in a lifetime of war", the camera focuses on Briseis' hair, and the netting from her wig/extensions is clearly visible.
When Hector removes his helmet right after Achilles does (during their fight scene), the nose bridge and flanks of his helmet move like rubber.
There were no countries in Ancient Greece. Priam and the rest of the Kings refer to their cities as countries but back then there was no such thing. There were known as 'City of Sparta' or 'Sparta', 'City of Troy' or 'Troy', Athens etc.
When Achilles came to the wall and was yelling for Hector, they could have had their archers take him out. They could have brought all of them up to the wall, but so Achilles couldn't see them, then they all could have stood up at once and fired at him. No way he could have survived. Of course, Homer didn't include that, so it would have been unfaithful to the original story.
Coins are placed on dead characters' eyes before their bodies are burnt. Ancient Greeks placed a coin in the corpse's mouth, not on the eyes. However, the Trojan War occurred before coined money was invented (in the 7th century BC), so they wouldn't have had coins at all.
Most equipment used by the Greeks, such as the large round shields and Achilles' helmet, is from the Classical Period (5-4th centuries BC). At the time when the epic is set, the Greeks used small bowl-shaped helmets and light leather shields shaped like the number 8.
When Hector's infant son sticks the lion in his mouth and pulls it away, the end of a modern pacifier is in the baby's hand.
When the Greek leaders are lining up to offer gifts to Agamemnon, one of them carries a red-figure vase shaped like a submarine. Red-figure pottery (made of red clay with a black glaze, from which lines and shapes are removed to make red images) was not made until the fifth century BC.
When Briseis asks Achilles if she is still his captive, her bikini tan line is very visible.
Throughout the film, whenever Hector, Paris, Achilles, and Menelaus all draw their swords, metal scraping can be heard as they are pulled from their shields. However, the interior of the shields are lined with cloth, and the loops that hold the swords are leather, not metal.
When Hector and Achilles fight, an obvious camera shadow appears on the ground.
In the Director's Cut, during the burning of Troy, a temple burns just after a statue falls forward and breaks. A crew member in a motorcycle helmet is on the roof, running across the top right-hand corner.
During the final battle in the city when a white horse is running down a corridor towards the screen a camera can be seen moving in from the left of the frame and then out again. Though it could be confused with a soldier's helmet, a green light is clearly visible.
After the Achaean fleet is spotted, villagers from the countryside begin pouring into the city. Among the animals being lead away is a pair of llamas. Llamas are originally from South America, and did not exist in Troy.
(at around 9 mins) Ships are shown under the caption of "Port of Sparta". Sparta is inland and near the center of the Peloponnesus; Sparta has no port.
(at around 17 mins) The caption "Mycenae" appears with a sea inlet in the background. Mycenae is inland and the sea cannot be seen from any vantage point near the city (ruins).
In the scene with Hector and Andromache right before the Greek ships arrive the sun is shown to rise above the ocean. Troy is on the west coast of Turkey so that sun should be setting.
After Achilles rescues Briseis from the Greeks' branding iron in the dark, they spend the night together. The next shot shows the sun rising over the sea, to the west.
When the boy goes to find Achilles to fight the warrior, he says "the Thessalonian is huge". He should have said "Thessalian". A "Thessalonian" is someone from Thessaloniki, a city that was founded centuries later (4th century BC) by Cassander, who became the king of Greece after Alexander's death. Cassander married Thessalonike, Alexander's sister, and named the city after her.
When the Greeks are sacking Troy towards the end of the film, you can hear a soldier (played by one of the the Mexican extras) yell "Aqui! Aqui!" (Here! Here!) twice.
When Paris goes to retrieve his sword after the death of Agamemnon's brother slain by Hector, you can see one of the soldiers fall down during the charge.