According to the lawsuit, the Vanity Fair and Rolling Stone photographer attacked James Parmenter at a Manhattan apartment in March 2012.
The suit was filed Wednesday in Manhattan Supreme Court.
It says Parmenter was chocked "to the point of unconsciousness."
The New York Post reports that LaChapelle's representative denied the allegations.
Paramenter has exhibited LaChapelle's works at his Bigfork Collaborations gallery where his prints go for more than $100,000 each.
LaChapelle has taken portraits of Elizabeth Taylor, Madonna and other celebrities.