The Oscar winner revealed Sheryl Berkoff gave her the fellatio talk when she was about 16 during a chat with Rob on his new podcast series, "Literally!".
Paltrow told the former Brat Pack icon she became obsessed with his wife-to-be when she was working as a makeup artist on one of her mother Blythe Danner's films.
"She (Berkoff) was dating Keanu Reeves, who was my celebrity crush, and she was so cool," Gwyneth told her longtime friend. "She knew that I was sneaking cigarettes, and she would come smoke with me behind the trailer."
"She taught me how to give a blow job... I just worshipped her. I thought she was literally the coolest chick of all time."
Rob, who married Sheryl in 1991, promoted his new podcast series by revealing one of the shows would feature Gwyneth, explaining, "No one is going to talk to Gwyneth Paltrow the way I do. I've known her since she was 16 years old, when she was staying in my guest house... while she was looking for an agent."