An architect and the son of a Swedish immigrant, Jens Fredrick Larson was 6 feet tall when he enlisted as a gunner with the Canadian Field Artillery on 10 August 1914. He sailed for France in February 1915, was promoted to Lieutenant on 19 August 1916, and transferred to the Reserve Brigade, Shorncliffe in September 1916. In December 1916, he was attached to the Royal Flying Corps and received training at the School of Military Aeronautics, Oxford University. He was posted to 8 Squadron on 5 May 1917, 34 Squadron on 26 May, and 84 Squadron on 8 August. One of the founding members of 84 Squadron, the unit deployed to France on 25 September 1917. Larson was promoted to Captain on 1 January 1918 and scored nine victories flying the S.E.5 before returning to England in May 1917. Injured in September 1918, Captain Larson returned to Canada in January 1919 before making his home in New Hampshire where he was architect in residence at Dartmouth College from 1919 to 1947.
Listed as Jens Frederick Larsen in several sources.