Wearing a red "Make America Great Again" hat, Trump, alongside his wife Melania, voted at a polling station in Palm Beach near his residence.
Speaking to reporters after casting his vote, Trump expressed that he was honoured to see the long lines.
"I feel very confident. You know, we went in with a very big lead today, and it looks like Republicans have shown up in force. So we'll see how it turns out. But it seems that they have really shown up in force," Trump told reporters.
The Republican candidate said he will monitor the election results from Mar-a-Lago, his resort and National Historic Landmark in Palm Beach, and claimed that he has a "substantial lead."
When asked if he told his supporters that there should not be violence related to the election results, Trump said he does not have to tell them that.
"Of course, there'll be no violence. My supporters are not violent people... And I certainly don't want any violence, but I certainly don't have to tell... These are great people," he added.
Trump also said he will accept the "fair" election results.
"If I lose an election, if it's a fair election, I'd be the first one to acknowledge. And I think it's been fair," he said.
Millions of Americans are voting to choose between Trump and his Democratic rival Kamala Harris for the 47th president of the US.
Voters are casting their ballots as Trump and Harris find themselves neck-and-neck heading into Tuesday's election. A compilation of polling from the RealClearPolitics website has Harris ahead by just 0.1 per cent nationally after she gained ground in recent weeks against Trump, erasing his one-time lead.
--BERNAMA-ANADOLU
