In the top of the eighth inning with reliever Miguel Batista on the mound, Zimmerman flied out to right fielder Lucas Duda, with Wilson Ramos scoring on the play.
Zimmerman became the seventh player -- Tim Wallach, Andre Dawson, Gary Carter, Vladimir Guerrero, Tim Raines and Jose Vidro are the others -- in franchise history to collect 500 or more RBIs.
"They are some really good players," Zimmerman said after the game. "Any time you are ever put in the same list as anyone who has been a great player in this game, it's very humbling. It makes all that hard work pay off."
Zimmerman said he didn't know he was close to reaching the milestone.
"Anytime you are lucky enough to play this game long enough to do something, I guess it's pretty cool. It's very humbling. Hopefully, I'll have a few more 500s," Zimmerman said.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.