Having started his career at Garioch RFC, Stephen played for his school team Glenalmond College before having his first taste of adult rugby at Aberdeen Grammar Rugby.

In 2023, he represented Scotland U18 in the 2023 Under-18 Six Nations festival before travelling to New Zealand to play for University of Waikato. He returned to Scotland to play for Scotland U20 in the 2024 World Rugby U20 Trophy.

He made his senior professional debut for Glasgow Warriors away to Leinster in Round 18 of the BKT United Rugby Championship, before going on to make 17 appearances in his first full campaign with the club.

His form saw him earn a first-ever professional contract with the Scotstoun outfit in April 2026, having received a first call-up to the Scotland squad the previous month.