The soul singer plays Venus Club owner Justice Charlier in the upcoming comedy musical, while Cruise plays rock band leader Stacee Jaxx.
Blige explained that she was not expecting Cruise to be able to sing as confidently as he does in the film.
"Nobody knew [he could sing]," she told Daybreak. "I was so shocked and surprised to hear him sound like the record, I was so impressed."
She also said that she was touched to have been given such great support from Cruise for one of her first major screen acting roles.
"Everyone was so supportive on this set. Tom was supporting all of us, and for him to support us in the way he did meant so much to me."
The singer added that she drew upon her own personal experience to play the role of Justice, who takes female lead Sherrie Christian under her wing in the film.
"There were women that helped me when I was rebellious at 17, who told me I was beautiful and smart," she said.
Rock of Ages opens in UK cinemas on June 13 and in the US on June 15.
Watch the trailer for Rock of Ages below: