The 21-year-old earned his first senior Scotland cap in the 15-13 victory over Australia at BT Murrayfield.
The hooker made an immediate impact with a magnificent finish to touch down for the game-deciding try on his debut.
Born in Toronto, Ashman qualifies for Scotland through his Edinburgh-born father, representing his country at U16, U18 and U20 level prior to his senior bow.
The hooker possesses an eye for the try-line, touching down 11 times in his 15 appearances for the U20s and finishing as joint top try-scorer at the 2019 World Rugby U20 Championship in Argentina.
He initially came through the ranks at Sandbach RFC, with former Warrior and current Sale and Scotland winger Byron McGuigan amongst the coaching team at the Cheshire club at the time.
The switch sees Ashman reunite with former Scotland U20 team-mates including Ross Thompson, Rufus McLean, Rory Darge and Ollie Smith, with the hooker providing cover in the front-row following an injury to Fraser Brown, who is expected to be out until the beginning of the New Year.
"I'm buzzing to come to Glasgow," Ashman told glasgowwarriors.org.
"The way the club play - the intent they have to move the ball and run with the ball - suits me down to a tee and is exactly the way I like to play.
"The young group of players coming through right now is really exiting, with the likes of Ross Thompson, Rory Darge and Rufus McLean all having made an impact in the last year. You can see they're building something at Glasgow and it's something I want to be involved in.
"I'm going to take this opportunity with both hands, and play as well as I can while at Glasgow."
Head Coach Danny Wilson added: "Ewan is another exciting young Scottish talent that has been stepping up and impressed recently for Scotland, as well as previously for the U20s.
"We're looking forward to welcoming him into our environment as we prepare for our next block of fixtures."