The alleged incident occurred at the Plaza Hotel at around 8 p.m. Saturday, according to a law enforcement official briefed on the case.
Spitzer, 56, and the woman -- identified by ABC station WABC as a 25-year-old -- had "some sort of romantic relationship for about two years," and it appeared she was going to break up with him, which "may have led to the spat," the official said.
The woman sustained no injuries of substance but was hospitalized to be treated for a non-serious cut on her arm and later released, the official said. The injury was not sustained in the altercation, the official said.
The woman identified Spitzer as her assailant, but then decided she did not want to press charges, though detectives were continuing to investigate, the official said.
Lisa Linden, a spokeswoman for Spitzer, said "there is no truth to the allegation."
Spitzer's lawyer also claims the alleged victim sent an email recanting her story, but ABC news has not seen the email and thus can't confirm its authenticity.
Spitzer, who was New York State attorney general before being elected governor in 2006, was forced to resign in 2008 after an investigation into a prostitution operation identified him as "Client 9," who had spent $15,000 on call girls. Investigators found he had spent no public funds on prostitutes, and he faced no charges in the case.