Driver Brian Weatherall, 45, had been driving over Kirkstone Pass in Cumbria when he had to slam the breaks on.
During the 37 second footage, a dark image of the aircraft comes quickly through the fog while almost skimming the stone wall.
The helicopter is believed to be a SAS chopper carrying out manoeuvres in the treacherous conditions.
Describing the moment, civil engineer Brian, of Durham, North East, said: "I just couldn't believe it, I've never seen anything like it.
"I was on holiday at the time and the roads were bad so I was taking it steady on the steep hill.
"It happened about 2pm and I had the whole family in the car, it really was quite something - and a lucky escape."
Brian said after he realised the near miss he said it was "pretty awesome" to witness such an event.
He added: "It does make you feel safe when you see how our forces can fly a helicopter."
The British Special Forces have been contacted for comment.