Rymer-Jones was promoted lieutenant in August 1917 and became an acting captain while serving as brigade adjutant from September 1918 until July 1919. In 1919 he served with the British Army of the Rhine and in 1920–1921 was in Ireland attached to the King's Own Royal Regiment. In 1921 he briefly served in Upper Silesia during the plebiscite and then went to Egypt as a staff officer until 1925. From 1927 to 1928 he served as a staff officer with the Shanghai Defence Force and his last years in the Army, from 1929 to 1933, were spent as a company commander at the Royal Military Academy. He was promoted captain in February 1929.