Continuity mistake: In the first battle where Wallace is attacking the palisades and he is riding slowly, pretending to be unarmed and later draws a morning star/flail from behind his hair, the morning star/flail obviously isn't there until he needs it.
Revealing mistake: During the first large battle between the Scots and the English, there is a clear, quick shot of an English soldier getting quite eviscerated on the right side of his body. For a fraction of a second, you can see a couple drops of blood splatter against some sort of protective glass between the camera and the soldier.
Continuity mistake: When Wallace is a boy and they are at the grave to bury his father and brother, the shovels of dirt shake the wrapped dummy body in the grave.
Audio problem: At the end, when the sword is thrown and sticks into the ground, the sound of the sword sticking into the ground is not synced up with the impact.
Character mistake: At the beginning, in the funeral of the young lady, the priest says in Latin the traditional "In nomine patris et filii et spiritus sancti", but he says the last word wrong, "sanctus" instead of "sancti."
Other mistake: Near the end of the battle of Sterling after Wallace nearly hits one of his allies on the horse, look on the right side of the shot. An English man wearing metal armor is fighting some Scots. He doesn't make much effort, barely swinging his sword. The Scots fighting him also don't put up much of a challenge either.
Revealing mistake: In the scene where Wallace comes back (right after his wife is killed), he throws two archers out of the tower. The second archer is supposedly killed on the palisade wall; but right before the camera changes, you can see the wall bending as he lands on it.
Continuity mistake: When the English and the Scots come together at the Battle of Stirling look at one of the Englishmen's swords: it is bloodied even though he has just engaged the enemy.
Continuity mistake: In the scene where Longshanks returns from France, confronts Prince Edward, and the soldier has left the basket with the head of the Prince of York, Edward reaches to remove the cover with his left hand, his right hand is on his hip. When the angle changes he is lifting the cover off with his right hand and his left is on his hip, when the angle cuts back, his right hand is back on his hip and his left hand is moving away from the basket. (01:41:30)
Continuity mistake: During the funeral for Wallace's father and brother, various people change positions. Murron starts out in front of her mother, frame left, then is in front of her father, frame right, then is back in front of her mother. Campbell and Hamish start out beside Wallace, jump to about 18 apart, then behind Wallace, then back to about 18 inches apart. (00:10:40)
Continuity mistake: When Wallace was in the bedchamber of a noble lord, he takes out a chain with a ball at the end. The chain is wrapped twice around his fist, and the ball is dangling under his fist; however, when Wallace swings the weapon, the chain is leading outwards from the top of his fist.
Continuity mistake: During the execution scene when Wallace is reflecting and sees his wife in the crowd. Pay attention to the axe as it is coming down on Wallace's neck. As the axe approaches, it slows down as it gets closer. The scene is in slow motion, so look close. [According to Mel Gibson, the executioner actually placed the axe near Wallace's head and then raised the axe. The scene was shot in reverse for the movie. Doesn't make it less of a mistake, but explains it - the axe was accelerating, so in reverse it looks like it was slowing down]
Continuity mistake: At one point, when a bit player escorts Wallace's friend away, he utters his only line without a Scottish accent. Someone from southern California must be visiting Wallace's army.
Continuity mistake: When Wallace is at his brother and father's funeral at the start of the film, Hamish's and Murron's father are both in attendance. Let's say that this is about 20 years prior to the first battle at Stirling in 1297. 17 years later, the battle at Bannockburn takes place, yet Murron's father is fighting in it, looking not a day older than at the funeral scene which was supposedly almost 40 years prior to it. And when Hamish's father dies at Falkirk, he looks no older than at the aforementioned funeral scene. A miracle anti-ageing cream perhaps?