A publicist for Moon's company, Sports 1 Marketing of Irvine, Calif., did not return phone calls or an email seeking comment.
The plaintiff, Wendy Haskell, 32, was hired as Moon's executive assistant in July and traveled with him on a weekly basis for speaking engagements, charity events and personal appearances, according to the lawsuit. She alleges that she was demoted by the firm in October after she complained about Moon's sexual advances.
After leading the University of Washington to a Rose Bowl victory in 1978, Moon played six years in the Canadian Football League followed by 17 seasons in the NFL.
He starred for the Houston Oilers from 1984 to 1993, when he set numerous passing records, and also played for the Minnesota Vikings, Seattle Seahawks and Kansas City Chiefs during his career before retiring in 2001 at age 44.
In 1989, he received the NFL's Walter Payton Man of the Year award for his charitable works and excellence on the field. But his reputation was later marred by scandals involving women.
In May 1995, he was sued by a Vikings cheerleader who accused him of sexual harassment, alleging that he offered her cash for sex. The case was settled out of court days later.
Two months after that, Moon was arrested in Texas after the quarterback's wife, Felicia, told police that he had slapped and choked her in their mansion near Houston.
Moon told reporters that the couple had an argument and that he had made "a tremendous mistake." He reconciled with his wife, who declined to press charges.
Authorities in Texas charged Moon with assault anyway, but he was acquitted by a jury after his wife testified that she had provoked the fight. They divorced in 2001.
Moon co-founded Sports 1 Marketing in 2010 and serves as its president.
According to the new lawsuit, Moon required Haskell to stay in his hotel room during business trips, sleep in the same bed and wear "skimpy thong lingerie bottoms" as nightclothes. When she protested, he replied that she had to comply to keep her job and said that "his prior assistant accepted the same arrangement," the lawsuit states.
Haskell declined to comment through her attorney, Diana L. Fitzgerald of Miami. The Washington Post does not ordinarily name alleged victims of sexual assault, but Fitzgerald said her client had agreed to go public.
Fitzgerald said Haskell did not report any of Moon's conduct, including the alleged sexual battery, to police. "I think she was scared," she said.
"She was expecting to further her career in the sports marketing industry," Fitzgerald added. "She had no idea that her job duties were going to involve that kind of perverse protocol."