Continuity mistake: At the battle of Jerusalem, the Muslims walk past 2 piles of rocks painted white, but both piles are the same pile - shot reused. Another reused shot was the firing of harpoon arrows with ropes attached, into the siege towers, all harpoons are the same harpoon.
Other mistake: At Kerak, as the 2 armies are facing off, the wind is blowing the banners of Saladin's army hard to the left, but as the view switches to Baldwin's army, facing the opposite direction, their banners are also blowing left. (01:33:00 - 01:33:50)
Factual error: Balian is depicted in the start of the film to be from France. He was actually a Poulain, a Frank having been born in Outremer.
Factual error: In the beginning of the movie during the burial scene, it looks like a modern community in the background.
Suggested correction: You don't see a "modern" community in the background. You see a few houses, but nothing to indicate anything that it's not part of that time period.
Factual error: When Balian arrives in Ibelin, on the wall inside the manor house, he's watching the painting depicting the Dance of Death, with the writing 'quod sumus hoc eritis'. However, the earliest known Dance of Death (Danse Macabre) paintings are from the first half of the 15th century. This motif developed during the late medieval period, inspired by the memory of the Black Death.
