As of Sunday morning, the former Massachusetts governor held a double-digit lead over his nearest pursuer, rival Newt Gingrich, as the totals mounted in a state where fellow Mormons accounted for roughly a quarter of all caucus-goers.
Returns from 16 of 17 counties early Sunday showed Romney with nearly 48 percent support, Gingrich with about 23 percent, Paul with 19 percent and Santorum with 11 percent.
"This is not the first time you gave me your vote of confidence and this time I'm going to take it to the White House," Romney told his supporters at a victory speech.
Romney won Nevada when he ran for president in 2008.
Gingrich and Texas Rep. Ron Paul battled for a distant second. Former Pennsylvania Sen. Rick Santorum trailed the field.
Romney went into Nevada, the first western state to vote, with big momentum from the Florida primary, which he won by a double-digit margin. That contest was as intense as Nevada's caucuses were sedate - so quiet that they produced little television advertising, no candidate debates and only a modest investment of time by the contenders.
In a state with the worst jobless rate in the country, Romney blasted President Barack Obama for his economic policies.
"America needs a president who can fix the economy because he understands the economy, and I do, and I will," Romney said.
Gingrich is still struggling after losing to Romney in Florida. He's facing a month of contests that favor Romney and only one scheduled debate, which have helped him in the past.
After losing Saturday, Gingrich vowed to stay in the race.
The Associated Press contributed to this report.