The 21-year-old has become a mainstay in the Warriors pack since making his competitive debut against Ulster in September 2016, making 50 appearances to date in a Glasgow jersey.
After signing his first contract with Dave Rennie's side in October 2017, the barnstorming ball-carrier made an immediate impression in his debut season as a professional.
The man from Perth was not only named as Most Improved Player of the Season at the club's annual awards dinner, but he also found himself the recipient of the Sir Willie Purves Quaich as the year's outstanding young Scottish talent.
Fagerson wrote his name into the Scottish rugby history books on Scotland's 2018 summer tour, making his debut against the USA in Houston to become only the third Scottish player in the professional era to earn senior honours whilst still a teenager. His debut also saw him become part of the 48th set of brothers to line up in the dark blue shirt, as he took to the field alongside elder brother Zander.
The back-rower continued to impress in 2018/19, starting each of Glasgow's final seven matches on their march to the Guinness PRO14 Final.
His displays in the Guinness PRO14 Final Series earned him a place in Gregor Townsend's wider training squad for the 2019 Rugby World Cup, claiming the man-of-the-match award in the semi-final triumph over Ulster at Scotstoun before producing a try-scoring display in May’s final at Celtic Park.
"I'm over the moon to be staying at the club," said Fagerson.
"It's been an amazing last few years for me, and the culture here is amazing. I'm excited to be staying on.
"We've got so much talent in this group that we're aiming for silverware - we were pretty close last year and we want to go one better this year."
Glasgow Warriors Assistant Coach John Dalziel highlighted the back-rower's potential following the announcement.
"Matt was superb for us in the closing stages of last season," said the former Melrose flanker.
"His dynamism with ball in hand and his work ethic around the pitch give us an added dimension to our attack, and his physicality is a real asset to our defence.
"The great thing for us is that, at just 21, he's only going to get better in the next few years and I'm excited to see what he's going to do in a Glasgow shirt."