The outspoken billionaire, 69, crushed closest rivals Ted Cruz and Marco Rubio to secure his third successive victory.
It takes the firebrand closer to becoming the Republican Party”s nomination for President.
His wins are a testament to his broad appeal among the angry voters making their voices heard in the election race.
The race for the Republican nomination now moves on to next week”s “Super Tuesday”, when 12 states will hold Presidential primaries.
He was mobbed by a crowd when he visited Palo Verde High School in Las Vegas before the vote.
The businessman ran through a list of campaign promises, including taking care of veterans and scrapping Barack Obama”s healthcare law.
He then posed for photos and greeted people who had lined up to meet him after they had cast their ballots.
He later claimed fraud could cost him the election, warning people to keep an eye out for “dishonest stuff” at their caucus sites.
Cruz, a fiery conservative, was looking for a spark to recover from a particularly rocky stretch in his campaign after winning the Iowa caucus.
He had a disappointing third in South Carolina after denying charges of dishonest campaign tactics and defending his integrity.