Zimmerman's contract will pay him $1 million in 2021, a source told ESPN after USA Today first reported.
Zimmerman opted out of the 2020 season because of concerns about his family's safety amid the coronavirus pandemic but is set to play his 16th major league season, all with the Nationals, who selected him with their first pick in the 2005 amateur draft shortly after the club moved to Washington from Montreal.
Zimmerman's future in Washington had been uncertain after the Nationals acquired Josh Bell to play first base, but Rizzo said last month that the team was open to bringing the 36-year-old back.
Zimmerman, a two-time All-Star, batted .257 with six home runs and 27 RBIs for the 2019 World Series champions.
While Zimmerman gave up a $2 million salary because he skipped last season, he did receive a $2 million buyout for the declined option at the end of his previous deal, which covered 2014 to 2019.
The Associated Press contributed to this report.