Federal prosecutors last month charged Paul Ceglia, 39, with faking a business contract that purported to show that Ceglia owned a large stake in Facebook. Ceglia had sued Zuckerberg in 2010 claiming he was owed the stake.
Wednesday's 30-minute arraignment hearing, before Judge Andrew Carter, was Ceglia's first appearance in U.S. district court in Manhattan.
Ceglia was arrested at his home in Wellsville, N.Y., last month. He was later released on bail.
He faces up to 40 years in prison if convicted on the charges of mail and wire fraud.
The case is USA v. Paul Ceglia, U.S. District Court for the Southern District of New York, No. 12-mj-01171.