Nolasco (10-12) retired 13 of the first 14 Washington batters and allowed only one runner to get as far as third base in racking up his third career shutout.
The right-hander scattered five hits, didn't issue a walk and struck out six as Miami took the opener of a brief two-game series at Marlins Stadium.
Ruggiano put Miami ahead to stay with a first-inning solo homer and added a run-scoring single while Giancarlo Stanton went 3-for-4 with three RBI as the Marlins banged out 13 hits.
Washington starter Stephen Strasburg (15-6) saw his personal four-start winning streak snapped, getting roughed up for seven runs (five earned) on nine hits over five full innings.
The National League East-leading Nationals dropped their fifth straight. The came into the game with a five-game lead over second-place Atlanta.