When Dustin Hoffman showed up at producer Joseph E. Levine's office for a casting interview, Levine mistook him for a window cleaner. So Hoffman, in character, cleaned a window.
During rehearsals of Dustin Hoffman's and Anne Bancroft's first encounter in the hotel room, Bancroft did not know that Hoffman was going to grab her breast. Hoffman decided to do it because it reminded him of schoolboys trying to nonchalantly grab girls' breasts in the hall by pretending to put their jackets on. When Hoffman did it, director Mike Nichols began laughing loudly. Hoffman began to laugh as well, so rather than stop the scene, he turned away and walked to the wall. Hoffman banged his head on the wall, trying to stop laughing, and Nichols thought it was so funny, it stayed in the finished film.
Robert Redford screen tested with Candice Bergen for the part of Benjamin Braddock, but he was finally rejected by director Mike Nichols. Nichols did not believe Redford could persuasively project the underdog qualities necessary to the role. When he told this to Redford, Redford asked Nichols what he meant. "Well, let's put it this way", said Nichols, "Have you ever struck out with a girl?" "What do you mean?" asked Redford. "That's precisely my point," said Nichols. Redford told Nichols that he perfectly understood the character of Benjamin, who was a social misfit. He went on and on about his ability to play the part. Nichols finally said to him, "Bob, look in the mirror. Can you honestly imagine a guy like you having difficulty seducing a woman?" The link between Nichols and Redford began when Nichols directed his first Broadway play, "Barefoot in the Park", starring the then little-known Redford.
Dustin Hoffman was told before his screen test that all of the other actors who had screen tested had agreed to a six-picture contract. Hoffman refused, telling his agent he would rather do it for free and not be obligated to appear in movies he didn't like. He ended up getting paid seventeen thousand dollars without further contracted films.
When Elaine tracks down Ben in his gloomy room and he causes her to scream, several other tenants gather behind the landlord in the doorway. One says, "Shall I get the cops? I'll get the cops." It's Richard Dreyfuss in one of his earliest film roles.