Cap badge The Reginai Rifles (Canada), 3rd Canadian Infantry Division

Details from the regiment were called out on service on 26 August 1939 and then placed on active service on 1 September 1939 as The Regina Rifle Regiment, CASF (Details), for local protection duties. The details called out on active service were disbanded on 31 December 1940. The regiment subsequently mobilized The Regina Rifle Regiment, CASF, for active service on 24 May 1940. It was redesignated the 1st Battalion, The Regina Rifle Regiment, CASF, on 7 November 1940 and embarked for Britain on 24 August 1941. On D-Day, 6 June 1944, it landed in Normandy, France as part of the 7th Infantry Brigade, 3rd Canadian Infantry Division, and it continued to fight in North-West Europe until the end of the war. The 1st Battalion was disbanded on 15 January 1946.

The regiment mobilized the 3rd Battalion, The Regina Rifle Regiment, CASF, for active service on 12 May 1942. It was subsequently redesignated the 2nd Airfield Defence Battalion (The Regina Rifle Regiment), CASF, on 19 July 1943 and served in Canada in a home defence role as part of Pacific Command. It was disbanded on 15 November 1943.

On 1 June 1945, a third Active Force component of the regiment, the 4th Battalion, The Regina Rifle Regiment, CIC, CAOF, was mobilized for service with the Canadian Army Occupation Force in Germany. The 4th Battalion was disbanded on 4 April 1946. The 2nd (Reserve) Battalion did not mobilize.

During the Second World War members of the regiment received 14 Military Medals with one bar to that award, seven Distinguished Service Orders, seven Military Cross awards, a British Empire Medal, an Africa Star, three French Croix de Guerre, and a Netherlands Bronze Lion. Many more were Mentioned in Dispatches.

The regiment suffered 356 fatal casualties by 7 May 1945.

Its first taste of combat came in Normandy, landing on Juno Beach on D-Day, during which it was the first Canadian regiment to successfully secure a beachhead. It later faced the 12th SS Panzer Division Hitlerjugend, which was almost completely annihilated by the British and Canadian forces. The regiment later entered Caen.