Rain had started on Saturday night, with heavy storms and wind in the forecast for the remainder of Sunday. No makeup date has yet to be announced, but the Nationals said it will be in the next several days.
The Marlins, who had lost the first two games of the series, entered Sunday 7-8 and 4 1/2 games behind the first-place Nationals (12-4) in the National League East.
Washington scored a 2-0 victory Friday night and a 3-2 win in 10 innings on Saturday.
The Marlins come back to Washington twice more this season, once in August and once in September. Both are set to be three-game series.
Miami manager Ozzie Guillen said that Josh Johnson, the scheduled pitcher for Sunday, will start on Tuesday in the series opener vs. the Mets. Everything else with the rotation should stay the same.
"We'd like to see JJ every five days," Guillen said. "I think he's back [on] track. We know this is a process with him."
Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.