Continuity mistake: The wagon, which is full of explosives, is on fire, so Mulan cuts Kahn (the horse) free with her sword and jumps onto Khan. She starts to ride away, while she holds the reins in her left hand and the sword with her right hand, up in the air. The wagon explodes and in the next shot, she still holds the reins in her left hand, though the sword, still in midair in her right hand, is now actually in its sheath, which is always attached to the left side of her belt. Some arrows are missing on the ground as well. Then her sheathed sword lands on the ground beside her. (00:53:45)
Continuity mistake: When Chien-Po causes everyone to fall down, rice flies out of the bowls of the people who were waiting in line for food, though their bowls were empty.
Deliberate mistake: During the movie, when Mulan is just a girl, you can see that her eyelashes extend beyond her eyes. When she is pretending to be a boy, her eyelashes are short (this makes perfect sense). But when she is in the medical tent her eyelashes are long even though she had no time to put on makeup. This is deliberate though, because without it she would have still looked like a boy, and just pulling her hair down wouldn't make her look any different (since that's how she looked in the pond). So they had to change her eyelashes to make her look more girlish.
Factual error: During the morning training session, Shang shot an arrow to the top of the pole so his soldiers can get it, but the arrow is stuck in a horizontal position. A difficult position to achieve, for someone shooting an arrow from below. Even if the arrow hit the pole at such a point in its arc, its kinetic energy would be at its weakest, preventing it from boring into the pole.