Hilton, 24, told police Lohan and her male friend approached him while he was at the party Thursday and the actress began screaming at him.
"You talk [expletive] about me to my boyfriend, this is what you get," Hilton said Lohan yelled out.
Hilton said the male friend proceeded to beat him up as Lohan laughed and egged him on.
Lohan's father, Michael Lohan, told TMZ his daughter had already left the party at the time of the fight and she didn't have anything to do with it.
A video exists, though, that appears to show Lohan interacting with Hilton moments after the fight outside the mansion, TMZ reported.
A second video appears to show Hilton confronting Lohan Friday morning about the incident, TMZ reported.