"I probably should have untucked my shirt, but I didn't," he joked, referring to closer Rafael Soriano's signature move upon the completion of a save.
Tyler Moore had two hits and drove in a pair of runs, and Washington relievers threw four scoreless innings -- the last one thanks in large part to Werth -- as the Nationals defeated the New York Mets 5-2.
Soriano got his ninth save after Werth's game-ending jumping catch against the right field wall on a drive by Daniel Murphy with two on and two outs.
"I think the rain might have knocked it down a little bit, give me a better chance at it. It was close," Werth said.
He wasn't sure if the ball would have made it out.
"In my heart of hearts, I knew it was going to be close," Murphy said. "(Soriano) crowded me just a little bit. He got it on me just a hair . Jason made a good play on it."
That brought up Murphy, who began play with a .337 road batting average.
"Murph's been one of their hottest hitters of late and he's one of their best hitters overall, so it's never comfortable when he's at the plate with a chance to tie the game," Nationals manager Matt Williams said. "But it's a game of inches sometimes and he didn't quite get enough of it."
Scott Hairston had an RBI double and a single for Washington, which has won nine straight against the Mets going back to last season, and was beginning a stretch of 15 of 19 games at home.
Nationals starter Tanner Roark (3-1) pitched five innings, giving up two runs on four hits.
The Mets snapped a 22-inning scoreless streak, their second longest of the season, with two runs in the fifth.
Jonathon Niese (2-3) took the loss, allowing five runs, three earned, in four innings. It was Niese's shortest outing since June 20, 2013 at Atlanta, when he left after 3 1/3 innings due to injury.
The Mets' defense hurt Niese early as the first three Nationals hitters of the game reached safely and scored. After Denard Span singled, third baseman Wright misplayed Anthony Rendon's grounder for an error.
Werth then singled home Span, and Washington added two more runs on a sacrifice fly and a fielder's choice grounder that might have been a double play. But the ball was bobbled briefly by second baseman Murphy.
"I just couldn't get into a rhythm, fell behind, wasn't able to execute pitches when I needed to," Niese said. "When that happens it's tough for the defense to stay on their toes when I'm working behind."
In the third, Hairston doubled home Ramos and scored on a single by Moore to make it 5-0.
Following consecutive shutout losses to the Yankees the Mets finally broke through against Roark.
The game was delayed briefly when a fan came onto the field near the Nationals' dugout and ran from first base around to home with one out in the ninth. He was tackled hard by a security person just behind home plate, drawing cheers from the crowd.
Washington selected the contract of 1B Greg Dobbs and optioned C Sandy Leon to Triple-A Syracuse prior to Friday's game. Dobbs, released by the Marlins on May 6, was signed as a minor league free agent Monday. To make room on the 40-man roster, the Nationals put Syracuse outfielder Eury Perez (broken toe) on the 60-day DL. . Manager Matt Williams said two Nationals on the DL, LF Bryce Harper (left thumb strain) and 3B Ryan Zimmerman (right thumb fracture), have doctor appointments next week and will get progress reports. . Mets RHP pitcher Jenrry Mejia, being eased into the closer's role, was unavailable after pitching the ninth inning Thursday night. "He hasn't been back-to-back in four years, so we've got to be careful," Collins said, adding Mejia will pitch consecutive games soon. . New York's Bartolo Colon (2-5, 5.84) opposes Gio Gonzalez (3-3, 3.97) Saturday.