The 24-year-old has been rewarded for a series of outstanding performances over the past 18 months, most recently his two-try showing in Saturday night's victory over the Dragons.
The news is the latest boost to the club ahead of the 2020/21 season, with the hooker becoming the twelveth player to re-sign with the Scotstoun outfit ahead of the new campaign.
Having made his club debut against Leinster in January 2018, Stewart put pen to paper on his first professional deal in December of that year after an impressive start to life at Scotstoun.
The former Dalziel hooker pulled on a Glasgow shirt 18 times in all competitions last season, including a try-scoring appearance in the Guinness PRO14 Final at Celtic Park.
A stellar year also saw Stewart earn his first senior international cap, coming off the bench against France in last August's Rugby World Cup warm-up match at BT Murrayfield.
The man from Carluke has made eight appearances for the club so far this season, as the Warriors continue to pursue a place in the 2019/20 Guinness PRO14 Final Series.
Speaking about his decision, Stewart said: "I'm delighted to sign up for another two years.
"It was an easy choice, really - this is a great club with a great group of boys, and it's a pleasure to come to work every morning.
"I want to get as much game time over the next couple of years and keep pushing forward as much as possible. The club's in a really good place right now and I want to continue to help us to move forward and challenge in the league and in Europe."
Glasgow Warriors assistant coach John Dalziel added: "We're lucky to have four excellent hookers with us in this playing group, and to have Grant committed for the next two years is a big boost for us.
"He's a really good young player and someone who deserves to be in and around the Scotland setup. He's had a great introduction to professional rugby over the last 18 months or so, and now we're looking for him to kick on. He's done really well for us and deservedly gained international recognition, and you saw what he's capable of on Saturday night.
"He's explosive and has really good footwork, and offers us a point of difference in our attack. He's a real asset to the club."