Cap badge The Queen's Own Rifles of Canada

The regiment mobilized for active service on 24 May 1940. It was then redesignated as the 1st Battalion, The Queen's Own Rifles of Canada, CASF on 7 November 1940. The unit served in Newfoundland (at the time a separate Dominion) in the defence of two strategic airfields at Botwood and Gander in Newfoundland from 10 August to 15 December 1940. After a build-up and training period, the unit embarked for Britain on 19 July 1941. The regiment mobilized the 3rd Battalion, The Queen's Own Rifles of Canada, CASF for active service on 12 May 1942. It served in Canada in a home defence role as part of the 20th Infantry Brigade, 7th Canadian Infantry Division. The battalion was disbanded on 15 August 1943.

For the Invasion of Normandy, the regiment landed in Normandy, France as part of the 8th Infantry Brigade, 3rd Canadian Infantry Division. The first major combat operations were on D-day 6 June 1944. The Queen's Own Rifles landed on "Nan" sector of Juno Beach and with the support of tanks of the Fort Garry Horsecaptured the strategic seaside resort town of Bernières-sur-Mer. The battalion fought its way to its D-Day objective - the village of Anisy 13.5 km (8.4 mi) inland, the only Regiment to reach its assigned objective that day. The QOR had the highest casualties amongst the Canadian regiments, with 143 killed, wounded or captured. As well as losses in the initial landing, the reserve companies' landing craft struck mines as they approached the beach.

In the battle for Caen, the QOR - as part of the 8th Infantry Brigade - participated in Operation Windsor to capture the airfield at Carpiquet which was defended by a detachment from the 12th SS Panzer-Division Hitler Jugend. The Germans inflicted heavy casualties and Panzer-grenadiers attempted to recapture the village

During the war, 463 riflemen were killed in action and almost 900 were wounded as they fought through Normandy, Northern France, and into Belgium and the Netherlands, where they liberated the crucial Channel ports. Sixty more members of the regiment were killed while serving with other units in Hong Kong, Italy and northwest Europe. The overseas battalion was disbanded on 30 November 1945.

On 1 June 1945, a third Active Force battalion, designated the 4th Battalion, The Queen's Own Rifles of Canada, CIC, CAOF, was mobilized for service with the Canadian Army Occupation Force in Germany. The battalion was disbanded on 14 May 1946.