With 99 percent of precincts reporting, the former Massachusetts governor won 59 percent of the vote, to 41 percent for U.S. Rep. Ron Paul of Texas, and was projected by CNN to have won based on exit polls and partial results.
Romney and Paul were the only two candidates who qualified for the GOP presidential ballot in Virginia.
Electoral analysts characterize Virginia as a swing state, in which no single candidate or party has overwhelming support.
Paul's strong finish was his best in either of his GOP primary campaigns by a long shot, and he was expected to capture some of the state's delegates, The Washington Post reported.
Virginia has 49 delegates to the Republican National Convention in August.
Thirty-three delegates are awarded on a winner-take-all basis by congressional district and 13 are awarded to the candidate who wins a majority statewide, or allocated proportionally if neither Romney nor Paul gets a majority.
Three so-called super delegates are not bound to any candidate.