The A-Team actor, who is believed to be dating Renee Zellweger, said that he had a bowl haircut that made him look more feminine at school.
Cooper told Details magazine: "I never lived the life of 'Oh, you're so good-looking.' People thought I was a girl when I was little, because I looked like a girl - maybe because my mother would keep my hair really long in a bowl cut.
"I was in a coffee shop once and the waitress was like, 'What do you want, Miss?' I was 10 or 11 - the worst age to have that happen. I had a jean jacket on and a Metallica pin. I thought I was really cool."