The 34-year-old Rivera is known for his defensive skills. He has thrown out 10 of 31 runners attempting to steal this season. He is batting .230 with eight homers and 23 RBIs in 54 games.
The Cubs lost catcher Willson Contreras to a hamstring injury on Aug. 9. They got Alex Avila in a trade with Detroit last month, and rookie Victor Caratini was promoted from the minors after Contreras went down, but the acquisition of Rivera gives them more insurance at the position.
To make room on the 40-man roster, right-hander Aaron Brooks was designated for assignment before Saturday's game against Toronto. The Cubs will have to make another move when Rivera joins the team.
To replace Rivera, the Mets recalled catcher Kevin Plawecki from Triple-A Las Vegas and activated left-hander Tommy Milone from the disabled list.
The 26-year-old Plawecki is 3 for 24 in 10 games with New York this season. He hit .328 with nine homers and 45 RBIs in 64 games for Las Vegas.
Milone had been sidelined by a sprained left knee. He is 1-2 with a 7.91 ERA in nine games, six starts, with the Mets and Brewers this year.