A product of Gala RFC, the 21-year-old joins Jack Oliver, Macenzzie Duncan, Matthew Urwin, Johnny Ventisei, Fergus Watson, Seb Stephen and Kerr Yule in making the step up this summer, as preparations continue for the new campaign.
Johnston made his Glasgow Warriors debut in February 2025, coming off the bench in a 45-20 win away to the Dragons.
His first start came earlier this season, lining up on the wing away to the Scarlets in round six of the BKT United Rugby Championship.
A former standout with Scotland U20, Johnston was invited to train with the senior Scotland setup ahead of the 2023 Rugby World Cup, whilst he also featured for Emerging Scotland against Italy in December 2024.
“I’m really grateful for the opportunity,” Johnston told glasgowwarriors.org.
“I’ve loved my time here so far, so the chance to have another two years in the environment is unreal. I’ve learnt so much so far and I’m excited to keep building.
“It’s really cool to see so many of the academy lads signing pro contracts at the same time. I’ve played a lot of rugby with guys like Fergus [Watson] and we’ve all spent time in the academy together, and we’ve really grown as a group. It makes the process so much easier when you’ve got such a good group around you.
“The coaching I’ve had here is the best I’ve had throughout my rugby journey so far. To be able to learn from the coaching team, as well as the world-class players we have here, is such a huge thing for me and I want to try and improve as much as I can by taking bits and pieces from everyone’s game.
“I just want to earn more opportunities for this club. If I can keep working hard and keep putting my hand up for game time, then hopefully everything else will follow suit.”
Head Coach Smith added: “Kerr is a young player we believe has real potential, as he continues his development with us at Scotstoun.
“He is a strong carrier with true top-end pace, whose ability to cover both centre and wing is a valuable asset to our squad.
“He is keen to keep on building his own all-round game, and we look forward to continuing to work with him for the next couple of seasons.”