The Washington Post reported that Rubio received 37.30 percent of the 2,839 votes that were cast. Ohio Gov. John Kasich came in second with 35.54 percent.
Billionaire Donald Trump came in third with 13.77 percent of the vote. D.C. Republican Party Chair Jose Cunningham told the Washington Post that U.S. Sen. Ted Cruz (R-Texas) came in fourth with 12.36 percent.
Primary voters cast their ballots at the Loews Madison Hotel on 15th Street, N.W., near Thomas Circle. The line to enter the polling place stretched around the block for most of the day.
Nineteen delegates were at stake in the primary.
The vote took place a day after Trump supporters clashed with protesters in Chicago after a rally for the Republican frontrunner was cancelled.
A handful of people stood outside the Loews Madison Hotel on Saturday with anti-Trump signs.