Continuity mistake: When Tina uses her psychic power to hang Jason, the size of the hole he falls through changes between shots.
Other mistake: When Melissa opens the front door and Jason is standing there, he raises his right hand, holding an axe, and plunges it straight down. But when Melissa has the axe in her head it is on the opposite side and at a different angle than it should have been. (01:13:45)
Continuity mistake: When Michael goes to the bathroom in the woods, Jane is standing next to the road. In the reverse shot, she is standing next to a tree.
Continuity mistake: When Jason shoves his fist through Dan in the woods his fist is bloody, but when he kills Dan's girlfriend, the blood is gone. (00:27:00)
Continuity mistake: When Jason swings the girl in sleeping bag against the tree, he grabs the head end, yet the head end is the one that hits the tree. [This is fixed and not a mistake in the uncut editions (theatrical and new release dvd) because the uncut scene has Jason taking six swings with the sleeping bag against the tree, including the head end.] (00:26:50)
Continuity mistake: When Tina battles with Jason, the height of the basement roof drastically differs.
Continuity mistake: When Tina is driving, she swerves to avoid Jason. The trees that she almost hits change between shots. (00:43:15)