Piazza hit two homers and drove in three runs for the Mets, who have won seven of nine games to move back over the .500 mark at 78-77 -- and out of last place in the National League East.
Winning pitcher Juan Padilla improved to 2-1. Aaron Heilman registered his third save.
Nick Johnson had two hits and three RBI for the Nationals, who have dropped seven of eight and replaced the Mets in the NL East cellar at 78-78.
Losing pitcher Travis Hughes, who gave up the homers by Wright and Jacobs in the eighth inning, fell to 1-1.