The hard-throwing right-handed pitcher allowed five hits and two runs, while tossing 11 strikeouts in six innings of work to earn his ninth win of the season. The 11 punch outs tied a season-high for Strasburg, who also fanned 11 batters on May 2 against the Pittsburgh Pirates.
Strasburg frequently used his two-seam fastball and changeup to dispatch of Marlins hitters.
"I'm just trying to execute pitches," Strasburg said. "When you get two strikes, you just want to try to put them away."
Bryce Harper did not officially log an at-bat in the victory, but reached on base in every plate appearances by taking five walks. Adam Eaton, Trea Turner and Anthony Rendon each had two hits in the victory. Catcher J.T. Realmuto and first baseman Peter O'Brien each had two hits for the Marlins, who tallied six hits as a team. Turner also robbed a base to pick up his 40th steal of the season.
"I think I stuck to my plan pretty well," Harper said. "I think if I would have swung the bat yesterday like I did today, I would probably have had nine walks in the series. I just have to try to wait for a pitch over the dish that I can drive. I wasn't able to get that today and was able to get on base five times."
Eaton plated the game's first run with an RBI single in the top of the second inning. Turner gave Washington a 2-0 lead with another RBI single in the next at-bat.
O'Brien sliced a home run just over the left field fence to cut the Nationals' lead in half in the bottom of the second frame.
"It has been impressive talking with [O'Brien] and watching his at-bats," Marlins manager Don Mattingly said. "He has a plan. You can tell he sticks to what he wants to do up there. He has some feel for what the pitcher is doing and he has a plan for what he wants to do with that."
Strasburgh ignited allowing the O'Brien home run. He hit Brian Anderson with a pitch before striking out Lewis Brinson, Austin Dean and Magneuris Sierra to end the inning. He returned to the bottom half of the next inning and struck out Sandy Alcantara, JT Riddle and Miguel Rojas for six consecutive punch outs.
The Nationals pushed the lead back to two runs in the top of the fourth inning on a sacrifice fly from Rendon. Realmuto then singled for the Marlins in the bottom of the inning before Strasburg issued a walk to O'Brien. He then struck out Anderson and Brinson, giving him a stretch of eight strikeouts of 10 Marlins hitters.
Realmuto brought in Riddle on an RBI single in the bottom of the fifth inning to make the score 3-2. But the Nationals answered back again in the next inning when Rendon plated Turner on an RBI single.
Nationals reliever Sean Doolittle slammed the door in the ninth inning with two strikeouts to earn his 25th save of the season.
The Marlins won Monday's game against the Nationals 8-5 to split the two-game National League East series. Miami hosts the Cincinnati Reds in a four-game series starting at 7:10 p.m. on Thursday at Marlins Park.
Washington returns to Nationals Park for its final home stand of the season, beginning with four-game series against the New York Mets. The Mets and Nationals begin that series at 7:05 p.m. on Thursday in Washington.
"Strasburg was huge," Nationals manager Dave Martinez said. "He came through. We needed him to go out there and at least give us six innings ... I told him that was fantastic."