The deal carries an average annual value of $5.875 million.
Pionk was slated to have his arbitration hearing Friday.
The 26-year-old Pionk had 32 points over 54 games with Winnipeg last season. Acquired in the 2019 trade that sent Jacob Trouba to the New York Rangers, Pionk has brought a surprisingly physical element to the Jets' backend along with his offensive skills, putting up 77 points across 125 games in two seasons.
Pionk's extension is likely the final piece of the puzzle in an overhauled Jets blue line, which saw the additions of Nate Schmidt from the Vancouver Canucks and Brenden Dillon from the Washington Capitals this off-season.
The Jets, however, still need to get fellow restricted free agent Andrew Copp signed. His arbitrating hearing is set for Aug. 26.