Reginald Scott Gardiner was born at Casterton, Victoria in 1893. He was a school teacher before enlisting as a private on 25 August 1914. Gardiner was made a clerk in the Divisional Headquarters, 1st Australian Division and departed Melbourne aboard HMAT Orvieto on 22 October 1914.

Gardiner went first to Egypt, where he was promoted to corporal on 1 March 1915, and then to Gallipoli via Lemnos. He witnessed the landing at Gallipoli on 25 April 1915 from aboard one of the transport ships. Gardiner was promoted to sergeant on 24 July 1915 while serving at Gallipoli. He was transferred to Egypt for duty on 2 October 1915 but re-joined his unit at Gallipoli on 18 October 1915. Gardiner left Gallipoli as part of the evacuation and, on return to Egypt, was transferred to 4 Section Medical, AIF Headquarters on 22 December 1915.

Gardiner left Egypt in June 1915 and was sent to England for officer training which resulted in his commission as a second lieutenant on 18 December 1916. He proceeded to France 16 January 1917 where he joined the 55th Infantry Battalion. According to his service record, Gardiner was "brought to notice of Secretary of State of War for valuable service rendered in connection with the war" on 24 February 1917. He was promoted to the rank of lieutenant on 22 May 1917. While in the 55th Battalion, Gardiner served both as a signalling officer and an intelligence officer. He also spent time between 25 April and 2 August 1918 attached to Headquarters, 14th Australian Infantry Brigade.

Gardiner left England to return to Australia on 25 February 1919. The medical history he provided on arrival in Australia indicated he was feeling fit despite the long war years during which he had suffered from influenza at Gallipoli in 1915 and was gassed in November 1917. He had not been hospitalised on either occasion. His appointment to the Australian Imperial Force terminated on 16 June 1919. Reginald Gardiner died on 14 November 1922.