Continuity mistake: Captain Willard's is not carrying a holster when he approaches the bridge and talks to Chief Phillips about him not pulling over the Vietnamese sampan or when he's tying his shoes as he sits on the front of the PBR. He never leaves the front of the boat to get his gun but as Clean starts machine-gunning the sampan he's wearing his holster.
Continuity mistake: Captain Willard and his two escorts get out of a helicopter and walk up to the guard post on the way to see General Corman. The soldier in the front is carrying some yellow papers in his right hand. In the next shot as they pass the guard the papers are in his left hand.
Continuity mistake: When we first see Captain Willard in the movie he's looking at the ceiling fan spinning above his head. There's only one fan above his head yet we see two different fans in the scene. The first ceiling fan has a different motor and the acoustic tiles show signs of water damage not seen on the second fan.
Continuity mistake: During the beach party Captain Willard shows a map to Colonel Kilgore who says, "it's hairy, got some pretty heavy ordinance". We can see behind the captain and the closest person is about fifteen feet away but in the next shot a soldier drinking a beer is behind the captain and Chief Phillips appears walking up behind the colonel.
Continuity mistake: When Clean first walks up to the sergeant about fuel for the boat there are two posters in the window behind him. The first time we see them their lit up but the second time six seconds later they're not and the blinds behind them haven't been touched. The only thing that's been changed is the stage lighting.
Continuity mistake: Chief Phillips yells, "You son of a bitch" as he shoots wildly. After he says this and Lance guns the engines look closely at the back of the boat because Chef is not at his machine gun. In the next shot he reappears where he should be firing the rear machine gun "Canned Heat".
Continuity mistake: Lance's Playboy bunny gets up and runs around after she's startled by Clean when he taps on the window. She accidentally knocks over a casket with a body in it. The first time we see the body there's nothing behind it in the casket but some dried blood. When we see it again four shots later the blood is gone and the body has some bandages or tape lying behind it's left arm.
Continuity mistake: When Clean sits down in the back of the boat and opens up the tape from his mom, notice the order of the bullets in the machine gun to the right of the screen. When we first see them they're all packed in order, three shots later as he reads the letter they're uneven though no one has touched them.