The magazine said DiCaprio was at a party at about 4 a.m. Friday at the home of Rick Salomon when a woman struck him with what appeared to be a beer bottle. Friends took the actor to a hospital where he received about a dozen stitches, People said.
Los Angeles Police Officer Jason Lee, a department spokesman, could not immediately confirm the report.
"I have received no notification of that sort. That doesn't mean that nothing happened, but normally we would get those kind of notifications here," Lee said.
A call to DiCaprio's spokesman, Ken Sunshine, was not immediately returned, but People said the spokesman had confirmed the assault.
"While leaving a small private gathering, Leo was attacked by a woman who was trespassing and had been repeatedly asked to leave the property," Sunshine told the magazine. "The attacker struck him with a glass object before being restrained by witnesses."
The attack was not expected to affect DiCaprio's work on a Martin Scorsese movie, "The Departed," which is shooting in Boston and New York, People said.