Investigators found insufficient evidence that Jackson, 26, attacked Supriya Harris of Mableton, Ga., in March 2009, Las Vegas police officer Barbara Morgan said.
"Our investigation is complete," said Morgan, a department spokeswoman. "I don't think the time passage was a factor here. We contacted the victim, the accused and witnesses. There's insufficient evidence to go forward with the case."
Morgan said the case will be closed and that records relating to the investigation wouldn't immediately be released.
Jackson's publicist, Steve Caric, said the running back had no comment.
Harris, 29, filed a complaint with authorities in LaPlace, La., on Jan. 27, alleging that the two-time Pro Bowl running back repeatedly pushed her to the ground and "flung" her against a door before his nephew intervened.
Copies of the report were posted online by CBS Sports and the celebrity Web site TMZ. In it, Harris said she was treated at a hospital for a cut on her hip from hitting a door handle.
Harris told police that Jackson later urged her to say she was injured during a fall in the shower.
Jackson issued a statement Jan. 28 through one of his agents, calling the accusations "untrue" and "hurtful."
Copyright 2010 by The Associated Press