A new collection of BBC interviews unearthed from the BBC archives shed fresh light upon the British director's real intentions.
Hitchcock, who died in 1980, said he actually intended 'Psycho' to be a "tongue-in-cheek" horror and was "horrified" by audiences' reactions.
The revelation promises to end decades of speculation among film buffs, who have long-argued about whether the movie was supposed to be a dark comedy or a "full-on" horror flick.Discussing the film on TV show Monitor in July 1964, Hitchcock said: "I once made a movie, rather tongue-in-cheek, called 'Psycho'.
"A lot of people looked at this thing and said what a dreadful thing to do, how awful, and so forth.
"The content as such was, I felt, rather amusing and it was a big joke. I was horrified to find that some people took it seriously."
The interview features in 'Alfred Hitchcock: In His Own Words', an audiobook re-released this week to coincide with the London premiere of 'Hitchcock', the new Hollywood biopic starring Anthony Hopkins.
The film, widely regarded as the world's first 'slasher' movie, terrified and shocked cinema-goers when it opened in 1960.
It contained unprecedented levels of violence and sexuality, and its infamous 'shower scene' -- of a woman being brutally murdered -- was later named the 'Best Death' in modern cinematography.
'Psycho', said to be Hitchcock's greatest-ever film, was adapted for the big screen from a novel based on the life of American serial killer Ed Gein.
It has grossed an estimated $80 million worldwide since its US release in 1960.
But Hitchcock says the film was never intended to be a 'proper' horror movie. He saw himself as a "switchback railway (rollercoaster) operator" who wanted to leave audiences "giggling with pleasure".
He told the interviewer: "It was intended to cause people to scream and yell and so forth, but no more than screaming and yelling on a switchback railway.
"I'm possibly in some respects the man who says in constructing it, 'how steep can we make the first dip?'
"If you make the dip too deep, the screams will continue as the car goes over the edge and destroys everyone.
"Therefore you mustn't go too far because you do want them to get off the switchback railway, giggling with pleasure."
Watch the trailer for 'Hitchcock'