The deal announced Tuesday will begin with the 2020-21 season and run through 2024-25. It carries an average annual value of $4.03 million.
Pettersson, 23, is in his second season with Pittsburgh after being acquired from the Anaheim Ducks on Dec. 3, 2018. He has 15 points (one goal, 14 assists) in 50 games this season and 34 points (three goals, 31 assists) in 107 games with the Penguins.
"In just over a year, Marcus has had a significant impact on our defensive group," said executive vice president and general manager Jim Rutherford. "He is young, reliable and smart, which is important in today's game. Marcus is part of our young core and it was important to get him signed long-term."
This season, Pettersson ranks fourth on the Penguins in hits (78) and blocked shots (57). He ranks third among Pittsburgh defensemen in points and is the only blueliner to skate in every game this season for the team.
A native of Sweden, Pettersson was drafted by the Ducks in the second round (38th overall) in 2014. He played in 49 games for Anaheim, tallying one goal and nine assists.
--Field Level Media