The deal comes into effect immediately and sees the former Scotland Under-20 captain commit to the Warriors until at least 2021.
The powerful 6ft 4in, 16-stone midfielder made his full Warriors debut against Southern Kings last season and has since gone on to play five times for the pro side, starting in the victories over Cardiff Blues, Ospreys and Scarlets in November.
The former Kirkcudbright Academy pupil and product of Stewartry RFC has represented Scotland at all age grades, skippering the Under-20s in this year’s junior Six Nations and World Cup. He said: “It’s a dream come true, being a professional rugby player is something I’ve always wanted to do.
“The last two months have gone by pretty quickly and I didn’t expect to get the run of games I got but I’ve really enjoyed it, especially playing at Scotstoun.
“My goal now is to get as much game time as possible, add consistency to my performances and learn as much as I can from the coaches and my team-mates.”
Glasgow coach Dave Rennie added: “He’s a big man with the ability to carry through contact, he’s incredibly fit and his distribution and kicking skills are also of real quality.
“He really impressed us during the international window, he looked really comfortable in the jersey and was never overawed by the opposition. We think he’s got a big future ahead of him.”