The deal, which is contingent upon Perez passing a physical, is worth $5 million, a source told ESPN's Buster Olney, confirming multiple reports.
Pérez, 32, won Gold Gloves in 2019 and 2020 with Cleveland but struggled at the plate throughout his career and hit just .149 with seven home runs and 17 RBI in 44 games in 2021. The Guardians declined his $7 million option for 2022.
Pérez is a year older and considerably more expensive than Stallings, but the Pirates were able to flip Stallings -- who is under team control through 2024 -- for minor leaguers, the main focus of general manager Ben Cherington's franchise-wide reboot.
The trade left Pittsburgh, temporarily at least, without a catcher on the major league roster after Michael Pérez was outrighted to Triple-A Indianapolis last week.
Roberto Pérez will take over as the primary receiver for a pitching staff in flux. The Pirates used 17 different starters in 2021 and the rotation is a bit of a jumble, though Pittsburgh did sign veteran left-handed pitcher José Quintana on Monday to a one-year deal worth $2 million.
Pittsburgh's staff in 2022 will not include Chad Kuhl, their 2021 Opening Day starter. The Pirates did not tender the 29-year-old a contract after he went 5-7 with a 4.17 ERA in 28 games (14 starts) last season, his first full season after undergoing Tommy John surgery on his right arm in 2018.
The Pirates did avoid arbitration with shortstop Kevin Newman, agreeing to a one-year deal worth $1.95 million. Pittsburgh also extended contract offers to All-Star center fielder Bryan Reynolds and pitcher Chris Stratton.
Information from The Associated Press was used in this report.