The bombastic real estate magnate, who is leading the polls among 17 Republican candidates for president, arrived at New York State Supreme Court at 9:08am (1308 GMT) dressed in a blue suit and striped tie.
He strode up the sweeping steps of the court house surrounded by a phalanx of police, television cameras, journalists and photographers, signing an autograph for one fan and fist-bumping another.
Joe Lepore, a New York tour guide, was ecstatic that former reality TV star fist-bumped him upon seeing his small, handcrafted sign of support.
“2016 all the way, Donald. It’s going to be a landslide,” he shouted as Trump marched into court.
Trump’s limo remained parked outside the court house, a rare sight on a street where parking is normally heavily restricted.
Monday’s civic duty marks a break for the billionaire’s campaign for the White House, where he has delighted supporters but enraged others with trash-talking comments about Mexican immigrants and with a crude remark about a female debate moderator.
He spent the weekend leading a rally in New Hampshire before attending the Iowa State Fair where he offered free rides for children in his helicopter.