Continuity mistake: As Captain Willard approaches Lieutenant Colby there is a woman standing in the crowd to the right of him. The next time we see him a few seconds later everyone in the shot is standing in the same spot except the woman is gone and a man wearing a green beret appears in her place.
Continuity mistake: As the boat leaves the USO show at Hau Phat Captain Willard says, "The war was being run by a bunch of four star clowns who were gonna end up giving the whole circus away". He says this as he walks to the back of the boat moving the 60 caliber machine gun on his way so that is faces frontward. In the next shot it's been moved and is now facing sideways.