Continuity mistake: Close to the end when Edward Norton runs up to the front of the empty building and Brad Pitt appears, he tries to break the glass door by pushing a bench into the door, but it doesn't work. He doesn't move the bench and he then shoots at the glass and breaks it. When it shows him walking through the broken door, the bench has disappeared. (02:05:10)
Continuity mistake: When the Narrator and Bob are crying together at the support group, Bob is much taller than the Narrator. However, when the two meet in front of Marla's place and Bob tells the Narrator that he is a member of Fight Club, the Narrator is taller than Bob. Edward Norton mentions this on the commentary. He is actually taller than Meat Loaf, but Bob is supposed to be taller than the Narrator. It seems they didn't remember to make him taller in every scene though.
Continuity mistake: Check out the sweat stain around the collar of Ed Norton's t-shirt in the scene towards the end of the film where he is being interrogated by police. It keeps getting bigger and smaller from shot to shot. (02:00:50)
Continuity mistake: When Ed Norton is blackmailing his boss the thermostat changes from white to black in some of the shots. The chair moves a bit to the left too. (01:16:00)
Continuity mistake: When Tyler gets beaten up by Lou, his mouth is bleeding after the first punch. After maybe two punches Tyler jokingly claims to "get it", then he says he "lost it". Right then the blood is no longer there. (01:12:25)
Continuity mistake: In the scene in the bar right after Edward Norton's apartment blows up, watch the men playing pool behind him. Towards the end of his conversation with Pitt, there is a continuity error. One of the men is bent over getting ready to take a shot. A mere second later, he's on the other side of the table and his opponent is finishing his own shot. (00:29:40)
Continuity mistake: Near the end of the movie in the underground car park, Brad Pitt pushes Edward Norton into the wingmirror of a van. The mirror flips back against the van and stays there. A couple of shots later we see Brad Pitt check his face in the mirror, which is at a different angle to what it was before. (02:08:45)
Continuity mistake: Near the end of the film when Tyler throws Ed Norton down the steps we get the view from a security camera, however we can see the camera we are supposed to be looking through in the top right hand corner. (02:09:10)
Continuity mistake: When they are preparing to confront the City Councilman, Brad Pitt's character pulls him in to the bathroom. If you really look at the locks on the door you see that as he is pulling him in there is no deadbolt lock, but when the Councilman is halfway in through the mirror you can see that the same door has a deadbolt lock. (01:33:45)
Continuity mistake: When Tyler Durden goes to Marla's apartment to prevent her suicide, he removes a cigarette from his mouth and gestures as if he is throwing it down on the floor at the top of the stairs. Then the cigarette is back in his mouth when he proceeds to the door, at which point he really does throw it down on the floor. (00:50:30)
Continuity mistake: When the narrator first meets Bob, Bob starts telling him how he used steroids. In one shot we see the narrator's right hand is resting at the middle of Bob's back, but in the next shot we see his right hand at the top of Bob's back and a little above his armpit. (00:08:10)
Continuity mistake: At the end of the film, when Ed and Brad are fighting in the parking garage, as Brad punches and throws Ed around like a rag doll, Ed's face goes back and forth between being caked in blood and being clean from shot to shot.