Henderson was born in Hong Kong in 2000. His Scottish father, Russel, was resident in Hong Kong working as a loss adjuster.[2] He started his rugby union career in Hong Kong as a colt for Hong Kong FC.[citation needed]
Henderson came to Scotland from Hong Kong in 2013.[3] He played rugby union for Strathallan School in Perthshire.[4] He was in the team that won the Scottish Schools Cup of 2017-2018 season, beating Glenalmond College in the final.[5]
Henderson graduated to be a Stage 3 player in the Fosroc Scottish Rugby Academy for the 2018-19 season. Stage 3 players are given a professional contract by the Academy. He was placed in the Caledonia academy and assigned to Glasgow Warriors for the season.[8]