The 23-year-old defenseman could have become a restricted free agent July 1. He signed a one-year, $874,125 contract Sept. 12, 2019.
"I feel very fortunate to have this opportunity," Pettersson said. "I felt like I said that before, that as soon as I got to Pittsburgh, this is a place you want to be with the history they have and the winning mentality, and the core group still here. I felt like this was by far the best option, and I haven't really thought about anything else but being here for a long time. I'm glad it worked out."
Pettersson has 15 points (one goal, 14 assists) in 50 games this season. He's averaging 19:22 of ice time and is the only Pittsburgh defenseman not to miss a game this season.
"In just over a year, Marcus has had a significant impact on our defensive group," Penguins general manager Jim Rutherford said. "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."