Pires was born on August 23, 1963 in Rio de Janeiro. She is the daughter of producer Elza Pires and actor Antônio Carlos Pires. She has a sister named Linda Pires, a therapist.
Glória made her debut as an actress at the age of 5, on the telenovela A Pequena Órfã, broadcast on the now defunct TV Excelsior. She initially participated only in the show's opening sequence, but director Dionísio Azevedo would later cast her to play a minor character. On her first day of shooting, however, she experienc