Eileen Berlin, a former film and theatrical agent in New York, signed Cruise soon after his 18th birthday and invited him to live in the home she shared with her late husband.
Speaking to The Mail On Sunday, Berlin revealed Cruise already knew he would be successful and acted outlandishly at times.
"By the time I met him, he had decided he could be a star. He wanted to be treated like a star and he acted like a star," she explained.
"He would walk around my house in a little G-string strap and nothing else. I had a mirrored wall and he would stand in front of it, flexing his biceps and admiring himself. I was a bit embarrassed but he liked to show off his body. He had a great pride in it."
Although she also admitted in the same interview that he could be a "moody" and "angry" young man, she added that Cruise was "sweet, respectful and mannerly to a fault".
Cruise parted ways with Berlin in 1983, but the 77-year-old stayed in touch and received invitations from the Church of Scientology once the actor started following the religion.
Last month, Cruise's third wife Katie Holmes filed for divorce after five years of marriage.
It has been suggested that Cruise's involvement with Scientology and plans for daughter Suri instigated the split, though the Rock of Ages star's lawyers have denied this.
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