Segundo was laid down on 14 October 1943 by the Portsmouth Navy Yard in [Kittery, Maine, launched on 5 February 1944, sponsored by Mrs. John L. Sullivan, and commissioned on 9 May 1944.

Segundo completed fitting out and contract trials then moved to New London, Connecticut, on 15 June and began training.

They refueled at Saipan on 3 September and departed the next day for their patrol area in the Philippines near Surigao Strait.

She was in the Philippine Sea 165 nautical miles (306 km; 190 mi) east of Catanduanes Island at 13°32′N 126°55′E / 13.533°N 126.917°E / 13.533; 126.917 on 13 September 1944 when two U.S. Navy planes mistook her for a Japanese submarine and strafed her as she crash-dived.

Segundo, and sister boats Trepang, and Razorback were cruising between Luzon Strait and the South China Sea.

This was done; and, after several trips between the two submarines by their respective representatives, the Japanese agreed to accept a prize crew aboard and to proceed to Tokyo with Segundo.

Segundo stood out of Tokyo Bay on 3 September 1945 en route to the west coast via Pearl Harbor.

She supported United Nations Forces in Korea from July to September 1950 before returning to San Diego in late November.

In 1951, Segundo was modernized and converted to a Fleet Snorkel submarine at the San Francisco Naval Shipyard.

The Segundo was ordered into port in San Diego and shortly after departed for Peal Harbor, then the north Pacific on a special patrol, submerging on 21 December 1956 and resurfacing on 21 January 1957 before stopping in Yokosuka Japan.