Raised on a dairy farm in West Linton, Paddy Harrison came through the ranks at West Linton Lions and Peebles RFC. He switched from the back row to hooker at Peebles, and made his senior debut for the club having just turned 17.

He went on to gain Super6 experience with Watsonians and joined the Edinburgh-aligned FOSROC Scottish Rugby Academy ahead of the 2020/21 season.

Harrison made his Edinburgh debut off the bench against the Dragons at the Principality Stadium in March 2021, aged 18, earning cap #1293.

In doing so he became the youngest hooker in club history, the third youngest in PRO14 history, and the club’s fourth youngest debutant of all time.

He made his first start in the Guinness PRO14 Rainbow Cup clash with Ulster that June. A prolific try-scorer at age-grade level, he scored eight tries in eight appearances for Scotland U20.

He made his breakthrough at senior level in 2022/23. His first Edinburgh try came against Cardiff in October 2022.

He then grabbed an acrobatic score in the 1872 Cup decider that secured a vital losing bonus point, and a 78th-minute match-winner against Zebre Parma. That form earned him a four-year contract with his boyhood club in January 2023.

Harrison was rewarded with his first Scotland call-up for the 2024 summer tour of the Americas. He made his Test debut off the bench against Chile in Santiago and scored his first international try against Uruguay a week later.

He made his first Test start against Portugal at Scottish Gas Murrayfield that November. In the summer of 2025 he started for Scotland against the Maori All Blacks.