Plot hole: In this movie Goblin was able to sneak up on Peter. But in the previous movies Peter was able to sense danger from quite a distance away; Green Goblin from a few blocks and the train barricade from over a mile.
Continuity mistake: When Peter meets Mary Jane backstage after her first performance, her hands continue to move on and off of Peter's shoulders between shots.
Continuity mistake: During the scene on the bridge where MJ breaks up with Peter, MJ's hair is tied behind her head with a few wisps hanging down and her ears visible whenever she is shown from behind. However, whenever MJ is shown in her own close-up during the same conversation, her hair is down loosely and her ears are completely covered up.
Continuity mistake: During the final fight scene, Spiderman is talking to Mary Jane while Harry is flying around. There is a shot of the Sandman about to clap his hands together around Harry. As the scene cuts to Spiderman taking off to save Harry and cuts back, Sandman's hands are much farther apart than they were before the cut.
Continuity mistake: During the battle among Venom, Sandman and Spider-Man, we see a news reporter with an English accent. She is narrating the fight, standing to the immediate right of her cameraman, who is pointing his camera skyward, at the fight. The reporter begins voicing her concern over the outcome. There is a cut to a TV showing the news report, where we see her finish her thought. Except we see a head-shot of her, and not the shot of the battle we should be seeing, considering the positioning of the camera.
Continuity mistake: In Harry's hospital scene, in one shot there is a medical device with tubes next to his pillow. In subsequent shots there are tubes only minus the device. In a later scene, when Harry is getting his memory back, his reflection of the hospital scene again has the medical device.
Continuity mistake: There are several scenes in the film where Peter's 'Spider-Man' costume can be seen sticking out from the top of his shirt, both the 'normal' red/blue version and the black symbiote version. The spider chest-emblem is visible in each of these scenes, but the emblem is smaller and much farther up the front of the costume, almost near his neck. Invariably, whenever he switches into full 'Spider-Man' costume, the emblem has reverted to its original much-larger size and is much farther down the front of his chest, level with his pecs.
Continuity mistake: In the scene where Gwen sees Peter in the restaurant she places one hand on his shoulder. The camera cuts to Gwen's face and she has both hands clasped together in the shot. The shot cuts back out and her hand is instantly down on Peter's shoulder. It cuts back to Gwen one more time and both of her hands are back up near her face.
Continuity mistake: In the scene where Peter asks Harry to help rescue M. J. (from Venom and Sandman), a sitting chair appears to the left of the painting of Harry's father in the last shot of Harry. There was no chair in the other shots of this scene. The sitting chair was by that painting for all of the movie except those few shots.