Donald Dunbar Coutts was born on 29 April 1890 at Mysia, near Boort, Victoria. Coutts worked in the Melbourne Hospital before enlisting on 18 November 1916 with the Australian Army Medical Corps. Embarking on 23 November at Melbourne, Coutts arrived in France by April 1917 and was posted to the 6th Australian Field Ambulance in July. In September he was involved in the Battle of Menin Road.

In December 1917, Coutts was posted to the 24th Battalion as the Regimental Medical Officer, and was promoted to major at the end of January 1918. The battalion played its part in turning back the German offensive of March, and played a major role at Mont St Quentin by recapturing the main German strongpoint atop the summit on 1 September. Coutts was awarded a Distinguished Service Order for his efforts during the battle, during which he attended the wounded for fifty two hours straight. He was also mentioned in despatches during the war.

After the war, Coutts returned to Australia. He was discharged at the end of February 1920 and in August he married Alma Matilda Hansen. In 1928, he joined the Royal Australian Navy Reserve and was transferred in 1942 to the Royal Australian Navy Volunteer Reserve, eventually becoming a surgeon commander. Coutts was awarded the Volunteer Reserve Decoration in 1946 and was transferred to the retired list in 1948.

Coutts ran his own general practice at Williamtown, Victoria, from 1927 and was the honorary Medical Officer and Consultant Medical Officer at the Williamstown and District General Hospital. In 1939, he took on another role as Medical Officer of Health for the city of Williamstown. Coutts returned to the Western Front in 1971 as leader of the 2nd Australian Division, 1st AIF Veterans Pilgrimage to France, wehere he helped unveil the new Australian Memorial at Mont St Quentin. He was also active in the Australian Red Cross and St John Association, and for his service to medicine he was granted The Order of the British Empire - Member (Civil) on 1 January 1973. He died on 17 September 1975 at Camberwell and was buried at Inglewood Cemetery, Victoria.