Mason was commissioned at Norfolk Navy Yard 28 February 1920, with Lieutenant Carl F. Holden temporarily in command until 8 March.

On 15 October she departed Halifax for the British Isles, via St. John's, Newfoundland, arriving in the River Clyde, Scotland, on the 26th for service with the 11th Escort Group, Western Approaches Command.

During the early part of 1941 the Broadwater escorted convoys, carrying troops and military supplies, around the Cape of Good Hope to the Middle East.

Assigned to the Newfoundland Escort Force in July, the ship patrolled the North Atlantic and guarded convoys against the German submarine "wolfpacks" into the fall of that year.

Four officers and forty crew lost their lives including Lt. John Stanley Parker RNVR, the first American to die in action whilst serving under the White Ensign.