Police say Stephenson was taken into custody Sunday following a 5 a.m. fight with the woman in Brooklyn.
The woman was treated at a hospital for injuries sustained in a fall down a flight of stairs.
The New York Daily News was the first to report the arrest.
The Pacers, who selected the 6-foot-5 guard out of Cincinnati in the second round of this year's draft, issued a statement Sunday night acknowledging Stephenson's arrest.
"We have been made aware of a situation involving Lance Stephenson early Sunday morning in Brooklyn," Pacers president Larry Bird said in a statement. "We are currently in the process of gathering information and will have further comments as we learn more facts."
Stephenson, 19, has been charged with third-degree assault and is awaiting arraignment, according to the Daily News.
The Brooklyn native was drafted with the 40th overall pick by the Pacers after one year at Cincinnati where he averaged 12 points, five rebounds and two assists.
Stephenson has had prior run-ins with the law, most notably he was charged with sexually assaulting a 17-year-old girl while in high school in 2008.
Information from The Associated Press was used in this report.