The actress explained to Flicks and Bits that her passing interest in the filmmaker grew into wonderment while playing Vera Miles in the new movie.
"I had only known him through the legend of him, through this kind of mythology in the film world," Biel said. "This idea that he was kind of a dictator, that he was very black and white about things, that it was either a yes or a no - there was no grey area there [is what I knew]."
She went on to say: "I just don't feel like that's who he was anymore, I feel like there's so much more to this man, such a humility to him and an insecurity and a vulnerability to him. He had an amazingly compassionate sense of humour, which is what I think him and his wife shared.
"They shared a love of film and a love of laughter. He was funny and clever and dark and witty, and kind of perverted in a wonderful way. I didn't know any of that about him, so I really do feel like my mind has been blown after having done this movie."
Biel's co-star Dame Helen Mirren recently admitted that she was "arrogant" and "ignorant" when she auditioned for the real Hitchcock in the 1970s.
Hitchcock is now playing in the US and opens on February 8, 2013 in the UK. Watch a trailer below: