The 25-year-old has enjoyed a superb season in Head Coach Franco Smith's first campaign at the helm, becoming a fixture in the midfield in both the BKT United Rugby Championship and EPCR Challenge Cup this season.
A product of Stewartry RFC, McDowall has made 51 appearances to date in Glasgow colours, having made his professional debut at home to the Isuzu Southern Kings in October 2017.
The recipient of the Land Rover Young Player of the Season award in the 2018/19 campaign, the Dumfries-born centre was called into the Scotland squad for the first time ahead of the 2020 Guinness Six Nations.
His form this season also saw him included in the Scotland senior setup ahead of the 2023 Guinness Six Nations, one of 17 Warriors to be called up by Gregor Townsend for the championship.
A former Scotland U20 captain, McDowall has made 13 appearances to date this season, scoring six tries for Franco Smith's outfit and winning the McCrea Financial Services Warrior of the Month award in February 2023.
McDowall has also captained the club on four occasions thus far in the campaign, leading the squad for the first time in January's 40-26 victory away to USA Perpignan.
"I'm massively pleased to re-sign," the centre told glasgowwarriors.org following the news.
"To be able to continue to represent this club - my home club - is such a thing for me. I'm incredibly proud to represent this team and everyone that is part of it.
"Franco has been a huge influence on me. The whole coaching group this season has really instilled a lot of confidence back into me again, and playing on a regular basis is such an important thing for any player.
"It's also been really cool to captain this team this year. Growing up you dream of playing for Glasgow Warriors, but captaining them was never something that crossed my mind. For Franco to give me that opportunity was a real honour. We've got a great group of leaders throughout this squad, though, and that's absolutely key for us.
"I just want to say thank you to the fans, too - seeing them getting behind us home and away week in, week out is something that gives us a massive buzz, and I'm proud to represent them every time I step onto the field."
Head Coach Smith added: "Stafford is someone who has fully bought into what we are looking to build here at Scotstoun.
"He's a key member of both our attack and defence, and someone who helps to bring out the best of his fellow Warriors.
"We know that he is someone that will give his all for this club, and we look forward to continuing to see him develop over the next couple of years."