The 20-year-old - Warrior #320 - made the transition from the FOSROC Scottish Rugby Academy to a full-time professional ahead of the 2020/21 season, and has impressed Danny Wilson and his backroom staff in his debut campaign.
The deal marks the latest milestone in a whirlwind start to 2021 for the University of Strathclyde student, having made his professional debut, been invited to train with the senior Scotland squad and extended his contract all in the space of six weeks.
Competent at both wing and full-back, McLean has earned representative honours for Scotland U18 and U20 in his career to date.
It was with Scotland U20 he really began to turn heads though, dotting down three times in four games - including in a record win over Wales - during the 2020 U20 Six Nations Championship.
McLean's Glasgow Warriors debut came against Edinburgh in January 2021 in the club's closely fought 23-22 victory, which involved an impressive covering tackle from the debutant that denied his opposite number a try in the corner.
Welcoming today.s announcement, McLean told glasgowwarriors.org: "I'm chuffed to be extending my contract with the Warriors.
"Glasgow is renowned for developing young players, and I love the environment I'm in here.
"My Edinburgh debut was surreal and it felt different out on the pitch than I had expected. I had to tell myself it's another game of rugby and I felt I showed up well.
"Hopefully, there is plenty more game time to come."
McLean has not only caught the eye of Danny Wilson in recent weeks, but that of national team Head Coach Gregor Townsend, who invited him to train with the Scotland squad ahead of the Six Nations opener against England.
Of that experience McLean said: "The Scotland invitation was a massive surprise and I appreciated being involved.
"International rugby is another step up in speed and being exposed to that was insane.
The knowledge and experience of people I was around - the likes of Stuart Hogg and the others in camp - and learnings I took away from that opportunity and those individuals is irreplaceable.
"It's experiences like those that will be invaluable in helping me kick on with Glasgow too."
Head Coach Danny Wilson added: "Since I joined the club in June, Rufus has been a player that has impressed the coaches a great deal. He is a young player with a lot of talent, and I see him having a great future with Glasgow.
"Against Edinburgh he played very well in his debut, and it speaks volumes to his work ethic being handed the opportunity to experience the national team set up in the build up to a Calcutta Cup fixture.
"In recent weeks he has continued to train well and I look forward to seeing him contributing more in the weeks ahead."