Arbuthnott enlisted in the Calgary Light Horse, a unit of the Canadian Army, in February 1917. He was later a Lieutenant in the Welsh Guards. Arbuthnott served as Lord Lieutenant of Kincardineshire from 1926 to his death, was Convenor of Kincardineshire County Council in 1933, and served ten years in the House of Lords (1945–1955) as a representative peer for Scotland. He married Dorothy Oxley of Ripon.