It was their sixth win in a row.
Reyes hit a two-run single in a five-run fourth and his eighth-inning RBI single capped the scoring.
David Wright had two hits and two RBI.
Carlos Beltran, Fernando Tatis, Gary Sheffield and Luis Castillo all had two hits and one RBI, and Jeremy Reed added an eighth-inning RBI single for the Mets, whose last loss was 6-5 at Philadelphia May 2.
Beltran hit his 123rd in a Mets uniform in the fifth.
Winner John Maine (3-2) was touched for one run and three hits in six innings, including a solo homer by losing pitcher Paul Maholm in the top of the fifth.
Andy LaRoche had two of the other four hits for the Pirates, who have lost seven straight.
Maholm (3-1) was shelled for seven earned runs and 10 hits in five innings.