Buck joined the Atlantic Squadron after a brief period of trial runs. From February until June 1941 she was with the Pacific Fleet and then rejoined the Atlantic fleet serving on convoy escort duty between the United States and Iceland and along the eastern seaboard.
With the entry of the United States into World War II Buck continued to serve as a convoy escort, steaming from the seaports of the eastern United States to ports in Newfoundland, Iceland, Northern Ireland, North Africa, and the Caribbean.
On 22 August 1942 during one of these crossings, Buck was hit starboard side aft by MV Awatea while trying to escort another vessel of the convoy to her assigned station during a dense fog. The impact cut off about two-thirds through Buck’s fantail and broke her keel. Seven of her personnel were lost. The starboard propeller was inoperative and within a few hours the port propeller dropped off. The fantail section, which had been secured by lines and wires, had to be allowed to sink when it became apparent that it would damage the hull by banging and chafing. On 26 August Buck, under tow by Cherokee (AT 66), reached Boston where she underwent repair until November. Upon completion of repairs she returned to Atlantic convoy escort duty until June.
Arriving in North Africa 21 June 1943, she was assigned to patrol duty off Tunisia and Algeria and then participated in the invasion of Sicily (10 July–2 August 1943) carrying out bombardment, screening, and patrol duties. On 3 August, while escorting a convoy of six liberty ships from Sicily to Algeria, Buck attacked and sank the Italian submarine Argento at 36°52' N., 12°08' E., and took 45 of her crew as prisoners.
Returning to the Mediterranean in late September 1943, after escorting a convoy to the United States, Buck supported the invasion and occupation of Italy. On 9 October 1943 while on patrol off Salerno, Italy, Buck was hit forward by at least one and possibly two torpedoes from German submarine U-616. The damage sustained was so complete that the ship had to be abandoned within three minutes after she was hit and she sank a minute later. The loss of life was very heavy. Only 97 of her personnel survived. They were rescued by Gleaves and the British LCT-170.
Buck earned three service stars during World War II.