The extension begins next season and has an average annual value of $4 million.
The 23-year-old has tallied three goals and 31 assists since he was acquired from the Anaheim Ducks in December 2018.
This season, the Swedish national has one goal with 14 assists and is plus 4 on the season.
“In just over a year, Marcus has had a significant impact on our defensive group,” general manager Jim Rutherford said in a statement. “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.”