Trump traveled with his wife Melania and daughter Ivanka, who also cast votes, to his corresponding polling center in Midtown Manhattan a few blocks from Trump Tower at East 56th Street.
When asked on what his response would be if television networks declare Clinton victorious, Trump said "We'll see what happens."
"It's really good," Trump said after voting, presumably for himself. "Right now, it's looking really good."
Clinton voted -- also presumably for herself -- near her home in Chappaqua, 30 miles north of New York City, at about 8 a.m. on Tuesday, arriving with her husband, former President Bill Clinton, and shaking hands with supporters.
"We are feeling confident about the campaign we've run and our candidate's message to the American people. Looking forward to seeing what today brings," the Clinton campaign told NBC News.
Hours ahead of Trump's arrival to the polling station, the location temporarily hosted two topless protesters.
"Hate out of my polls," one woman had written above her exposed chest. "Trump, grab your balls," the other woman had written on her body, seeming to reference the recently released audio from 2005 in which Trump talks of grabbing women without their consent.
Secret Service and local police escorted the women from the polling place about 30 seconds after they removed their shirts.