Her 12th and last war patrol was carried out in the Nansei Shoto Islands. Departing Pearl Harbor December 26, 1944, she found no targets until January 24, 1945, when she intercepted a nine-ship convoy. On approach, she received an unexpected salve of 19 depth charges, went deep and was boxed in by four high-speed escorts. For two and one half-hours, the enemy above worked her over systematically, dropping a total of 95 depth charges uncomfortably close. Minor damage mounted as she was first shaken and later knocked down about 60 feet in the next to last attack. She evaded her pursuers after firing false target shells to confuse them.

GREENLING reached Saipan on January 27, 1945, for emergency repairs. From there she was routed onward via Pearl Harbor to San Francisco, then to Portsmouth, New Hampshire. After overhaul in the Portsmouth Naval Shipyard, she was decommissioned in New London, Connecticut on October 16, 1946, with 10 battle stars and the Presidential Unit Commendation.

GREENLING returning to the Submarine Base, New London
GREENLING returning to the Submarine Base, New London

In December 1946, GREENLING was placed in service of the First Naval District. Stationed in Portsmouth, New Hampshire, and later Boston, she continued a vital role of training the Organized Reserve. On March 18, 1960, she was placed out of service in the Boston Naval Shipyard, and she was sold for scrapping June 16, 1960, to Minichiello Brothers, Chelesa, Massachusetts.