Continuity mistake: The day after the USO Playboy Bunny show, the patrol boat canopy is set afire by some pranksters from a passing boat. Yet, that night in the scene at the Do Lung Bridge, the canopy is intact. It goes through some amazing transformations during the remainder of the picture.
Revealing mistake: In the major helicopter scene when Ride of the Valkyries is played, the actual tape isn't going over the playing heads.
Continuity mistake: In the first few scenes with the air cavalry commander, his black hat has a lieutenant colonel rank and a small crossed-sword emblem on it. Later, as his helicopter lands on the beach, his hat has no rank and is emblazoned with a very large crossed-sword Cav emblem.
Continuity mistake: After the helicopter attack when the chopper drops the patrol boat into the water, you can see the canopy and the radar type antenna break and collapse. When you see it again it's in perfect condition.
Factual error: When LtC. Kilgore requests the air strike, you can see that the F-5s are not carrying any ordnance under their wings, except for a centerline fuel tank. Also, their color scheme varies from a white to a greyish one.
Continuity mistake: As Chef grabs the black wig it's clear to see that the window on the helicopter door has a strain crack going down the middle of it. It's there for two shots then when Clean hammers on the helicopter door the first time it's not broken. After he climbs up onto the helicopter and bangs on the front windshield he comes back to the side window a second time and it's cracked again.
Continuity mistake: As they pull up next to the Vietnamese sampan Clean runs to the port side of the boat in order to catch the tow rope. Chef is standing behind Captain Willard in middle of the boat and doesn't move and all. In the next shot Clean and Chef are both standing on the edge of the port side of the boat.
Audio problem: Approaching Kurtz' compound Lance starts drumming on two tin cans and if you listen closely they get the overdub wrong. At first we hear two distinct pitches, which are the actual sounds, picked up by the microphone but the last time he hits it we hear a third higher pitch which was overdubbed. There are only two cans not three and he doesn't change the way he's holding them therefore you can only have a maximum of two audible pitches.