Originally, Beltran's shot to center field in the third was ruled a single and an error after Nationals center fielder Elijah Dukes misplayed the ball, allowing Luis Castillo to score. But the game's official scorer changed the ruling an inning later, crediting Beltran with a triple and his 1,000th RBI.
Beltran achieved the feat on his 32nd birthday.
Hank Aaron holds the all-time record with 2,297 RBIs, and Ken Griffey Jr. is tops among active players with 1,774.
Beltran is second on the Mets this season with 13 RBIs, and he ranks 10th in Mets history with 431 of them. The all-time Mets leader, Darryl Strawberry, is tied with Beltran on the career list with 1,000 RBIs.
Beltran also ranks behind teammate and countryman Carlos Delgado, whose 1,503 career RBIs are a record among Puerto Rican-born Major League players.
Anthony DiComo is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.