Following brief pauses for training at Key West, Florida, and in the Panama Canal Zone, she reached Pearl Harbor during the latter part of January 1945.

On 18 March, Tench received orders to take up lifeguard station off the western coast of Kyūshū during Fifth Fleet carrier air raids on Nagasaki.

Tench stood offshore and watched while they loosed their remaining bombs on installations near Akune: a railroad bridge, a fuel dump, and a factory.

In the absence of targets worthy of torpedoes, the submarine contented herself with the destruction of floating mines and with the sinking of two tiny trawlers on 28 March.

The fact the enemy ship carried radar, coupled with the appearance of a second target larger than the first, indicated she was some type of warship escorting a merchantman.

Tench’s report claims the target, the large cargoman, took one torpedo hit and erupted in a splendid pyrotechnic display.

American planners had foreseen the possibility of Japan's attempting to strike back at the Allied forces with what remained of the Imperial surface fleet.

She was on station off the western coast of the Japanese home islands when the Yamato task force sortied on 6 April to contest the Okinawa landings.

In accordance to orders, Tench cleared the area for an air-sea rescue sweep of the East China Sea before ending her patrol.

Refit completed and her crew rested, Tench (now skippered by Tom Baskett)[13] returned to sea early in May for her second war patrol.

During the waning days of May, she sighted little enemy shipping of consequence though her gun crews dispatched a number of motor luggers, picket boats, steam trawlers, and other small craft to the depths.

For five days, the submarine worked her way back and forth across the strait, dodging enemy patrols and picket boats but without finding suitable targets.

Tench sank the merchantman in a submerged attack and spent the rest of the day evading spirited and persistent enemy retaliation.

After firing a salvo of torpedoes at the enemy from her bow tubes, Tench put her rudder hard over to turn and retired rapidly.

During that escapade, her guns destroyed four schooners and severely damaged another five, along with a sea truck, a motor trawler, and some warehouses and other dockside installations.

Her last encounter of the war occurred on 9 August when she surfaced in fog to torpedo and sink a seagoing tug towing two large barges.

Following stops at Pearl Harbor and Balboa, Canal Zone, Tench moored at New London, Connecticut, on 6 October 1945 – a year to the day since she had entered commission.

Almost four years of idleness ended for Tench in October 1950, when she came out of "mothballs" to be converted to a Greater Underwater Propulsion Power Program (GUPPY) submarine.

On the night of 13 January 1955, Tench accidentally grounded herself in ten feet of water 1,500 yards due east of the Cape Henry lighthouse, a Navy spokesman said.

That employment continued until October 1961 at which time she stood out of New London on her second deployment to the Sixth Fleet in the Mediterranean from which she returned early in 1962.

During the late summer and early fall of 1968, Tench took part in a NATO exercise, Operation "Silvertower," in the eastern Atlantic.