Continuity mistake: When Bruce Willis shoots Alan Rickman, Rickman falls through the window and grabs Bonnie Bedilia's arm to pull her with him. He has a good grasp on her arm because of her watch. When Bruce Willis is trying to release the clasp on her watch, you see blood on her face from his arm. The shot then cuts to Alan Rickman, and when the camera goes back to Bedelia and Willis, there is no longer any blood on her face.
Continuity mistake: After he climbs out of the air duct, John McClane's shirt goes from white to green. The dirt and grime from the air duct would cause discolouration only where the shirt comes in contact with the duct. However, his shirt is uniformly green including places that wouldn't make contact and it is impossible for all surfaces to make contact even in small areas.
Continuity mistake: After the terrorists blow the roof and Willis jumps off with the fire hose, he hits the window. After kicking the window for a while, he decides to shoot it. As he pushes off the window you can see that his gun is out and pointed at the window yet in the next scene he pulls the gun from his side and then starts shooting at the window.
Continuity mistake: Takagi is sitting on the chair facing the door of the room when he is shot. In the next scene, the same door is splattered with blood, yet the glass structure which should be splattered with blood should be the glass window behind Takagi, not the door which he is facing.
Continuity mistake: When Bruce Willis breaks through the window (as the roof is blown), he lands on his back, head pointing towards the window. However the next moment we see him catching his breath, lying on his stomach and feet aimed at the window as the firehose hanger falls past the window.
Continuity mistake: When he's climbing down the vents, the strap unties, and Bruce Willis falls. He misses the vent he was reaching for, and falls past the next one, so we assume he catches the third one down. However, after he flicks off his lighter, the camera pans up from the lit vent to Karl, and we can see that he somehow grabbed and climbed into the vent he definitely fell right past in the shot from above.
Continuity mistake: In the scene where Al asks John if he has any kids of his own, John pulls out his wallet with a picture of his family. He is holding the radio and the wallet, but when it cuts to John's "Jungle Gym" comment, both his hands are on the wallet. It then cuts to John again holding the radio and the wallet.
Continuity mistake: When Argyle rams his limo into Theo, the limo and ambulance are pinned so the front of the limo is well in front of the ambulance door. However, when Argyle gets out and punches Theo through the window, he's standing where the limo should be, and not standing on top of it.
Continuity mistake: When the box truck (carrying the thief gang) drives down the ramp and the grey Mercedes continues on, you can see that the driver of the Mercedes is a white male without glasses. A minute later, the grey Mercedes pulls up to the front of Nakatomi Plaza. Alexander Gudunov gets out on the passenger side, and the driver gets out: he's now a black male with glasses.
Continuity mistake: Karl comes in to tell Hans that Marco is down on the street and that the bag is missing containing the detonators. Hans then picks up the radio and switches channels to talk to Theo. Right after that we hear Powell on that same channel trying to reach out to John. How could Al be on the same channel as Theo when Hans was just talking to John minutes before on a different channel?
Continuity mistake: When Argyle is sitting in the back of the limousine he hears on the news that terrorists have taking over the Nakatomi building and that their means of communication is through the use of CB radios that they brought with them. Argyle then moves to the front seat of the limousine and turns on the CB which is immediately tuned to that exact channel.
Continuity mistake: Argyle is seen driving the limo around the garage after hearing that the terrorists have taken over the building. During that scene there are a couple of shots where the back window does not show anyone or anything in the back. But after the limo stops, he looks in the rearview mirror and the bear is sitting with it's head over the back of the seat. This would have been noticeable in the driving shots.
Continuity mistake: In the scene where Sgt Powell is entering his patrol car after checking the building, you can see that the spotlight is missing from the car exposing the mounting holes. However, after the body has landed on his car and he retreats rather quickly, the spotlight is back on the car.