Between July 1943 and 22 April 1944 Buckley operated along the eastern seaboard as training ship for prospective officers and nucleus crews of other destroyer escorts.

On 22 April 1944 she joined hunter-killer TG 21.11 for a sweep of the North Atlantic and Mediterranean convoy routes. On the morning of 6 May aircraft from USS Block Island (CVE-21) reported an enemy submarine near Buckley. She steamed toward the surfaced submarine evading her torpedoes and gunfire, and commenced firing. At 0328 Buckley rammed the German submarine U-66 and then backed off. Shortly thereafter, the submarine struck Buckley, opening a hole in the escort vessel's starboard side. The U-66 drew astern of Buckley and sank at 0341 in 17°17' N., 32°24' W. Buckley picked up 36 German survivors and then retired to New York where she underwent repairs until 14 June 1944.

After completing refresher training at Casco Bay, Maine, in July 1944, Buckley escorted two convoys to North Africa (14 July-7 November 1944). She then operated on anti-submarine and convoy escort duty along the eastern seaboard and in the North Atlantic until June 1945. During this period USS Buckley and USS Reuben James (DE-153) sank the German submarine U-548 on 19 April 1945 in 42°19' N., 61°45' W.

Buckley escorted one more convoy to Algeria during June-July 1945 and upon her return to the east coast commenced conversion to a picket ship. In October 1945 she participated in the Navy Day ceremonies at Jacksonville, Fla., and then on the 31st reported to the 16th Fleet at St. John's River, Fla. Buckley was placed out of commission in reserve 3 July 1946. On 26 April 1949 her classification was changed to DER-51 and on 29 September 1954 she was reclassified DE-51.