The 'Born This Way' hitmaker said she was bullied when studying at New York University's Tisch School of the Arts in her hometown, as she addressed the crowd during a concert at Madison Square Garden.
Gaga told the crowd how drama teachers said to her: "You'll never be the heroine, the blonde, the star. Your hair's too dark. You look too ethnic."
She said she had replied to them, "What about Liza?" Referencing actress and singer Liza Minelli, who was in the crowd.
Gaga also paid tribute to her hometown during the show, her last in New York before her 'Monster Ball' tour finishes in May.
She said: "I used to live 20 blocks from here, so I saw all those names go up on the marquis, and I always wanted to see my name up in those lights.
"You made me brave, little monsters, and New York made me brave."
The 'Bad Romance' star also raged against lip-synching, saying "never have, never will. I won't be the b***h to lip-synch her way through an HBO special," in reference to a TV programme made by the US network about her 'Monster Ball' shows and filmed during her dates at the famous venue this Monday (21.02.11) and Tuesday.
Lady Gaga's HBO special is set to air in the US on May 7.