Soon after America's entry into World War II, Sylph was fitted with sound gear and depth charges and assigned to Tompkinsville, New York, to help patrol for German U-boats.

Future Hollywood actor Ernest Borgnine served as a U.S. Navy gunner's mate aboard Sylph during its antisubmarine warfare patrols of the North Atlantic.

Assigned to Quonset Point, Rhode Island, she gave her full attention to training sonarmen and to the development of equipment and techniques for finding and sinking submarines.

In October 1944, Sylph and her unit, the Surface Division of the Atlantic Fleet's Antisubmarine Development Detachment, shifted base to Port Everglades, Florida.

She continued to train sonarmen there and assisted in the antisubmarine warfare research effort through the end of World War II.