Trump received 304 electoral votes to Hillary Clinton's 224. Six "faithless" electors voted for other candidates, costing Trump two votes and Clinton four, CNN reported on Monday.
Hawaii's electors are still set to meet later Monday, with the state's four votes expected to go to Clinton.
The results mean Trump -- who lost the popular vote by more than 2 percentage points to Clinton -- easily staved off a long-shot bid by opponents to turn Republican electors against him.
The Electoral College results will be officially certified January 6 during a joint session of Congress.
"This election represents a movement that millions of hard working men and women all across the country stood behind and made possible. With this historic step we can look forward to the bright future ahead. I will work hard to unite our country and be the president of all Americans. Together, we will make America great again," Trump said in a statement.
He also claimed his win was "a historic electoral landslide victory in our nation's democracy," though Clinton actually won the popular vote by about 3 million ballots nationwide making Trump the worst-performing winner in the popular vote since 1876.
Trump was put over the top by electors in Texas. Thirty-six of the state's 38 went for Trump, while two ignored the state's Election Day results. One voted for Ohio Gov. John Kasich and one backed former Texas Rep. Ron Paul.
The first response from Trump's camp came from Vice President-elect Mike Pence, who tweeted: "Congratulations to @RealDonaldTrump; officially elected President of the United States today by the Electoral College!"
Pence also wrote: "I'm honored & humbled to be officially elected today as the next Vice President of the United States of America by the Electoral College."