It operated from late 1942 to January 1945 in the Mediterranean, European, and Pacific theaters of World War II.

The M6 saw limited use during the war, and was poorly suited to modern warfare as it was unarmored and was armed with a too small caliber gun.

The 37 mm GMC M6 saw limited employment with U.S. forces (the 601st and 701st Tank Destroyer Battalions) during the campaign in Tunisia in late 1942 and early 1943.

The vehicle was not well liked because it lacked armor and carried an anti-tank gun that was largely ineffective against German tanks of the period.

After the Tunisian campaign, many M6 Fargos had their 37 mm gun removed and reverted to a cargo truck role as the WC52.