He was born in Newtownstewart in County Tyrone before his family settled in Lurgan. He grew up idolising Tommy Bowe and Jonah Lomu.Gerry Thornley, "Jacob Stockdale living the dream playing alongside his boyhood heroes", The Irish Times, 11 November 2017 He attended Wallace High School in Lisburn, where he played in the back row before moving to centre. He played for the school's first team in his final year,Jack O'Toole, "Jacob Stockdale - From Wallace reserves to one of the best wingers in the world", Sports Joe, 2019 was selected for Ireland at Schools and under-18 level, and was named Ulster Schools Player of the Year in the 2014 Ulster Rugby Awards.Richard Mulligan, "Trimble celebrates hat-trick", News Letter, 5 May 2014
