Requin arrived at Staten Island, New York, on 18 September to begin what would be, in the words of Commander Cutter, "a dull and boring assignment," essentially becoming a target for sonar school ships.

August through November of that year was spent at the Portsmouth Naval Shipyard in Kittery, Maine, being converted to a radar picket submarine under project MIGRAINE.

After leaving the yard, she resumed operations in the western Atlantic and in the fall of 1947 moved north for exercises with her sister radar picket submarine Spinax (SS-489); on 13 November, she crossed the Arctic Circle.

Given hull classification symbol SSR-481 on 20 January 1948, Requin began modification to the MIGRAINE II Radar Picket configuration at the Portsmouth Naval Shipyard in Kittery, Maine.

During September, she visited the United Kingdom; then, in October, the submarine transited the Strait of Gibraltar for her regular Sixth Fleet duty.

In 1953, she maintained her schedule of Second and Sixth Fleet operations, but at the end of the year put into Philadelphia, Pennsylvania, for an extensive modernization overhaul that among other changes removed her last anti-aircraft cannon.

From June through August 1959, the Charleston Navy Yard in South Carolina removed all of Requin's radar equipment and improved her streamlining.

Upon her conversion to Fleet Snorkel configuration, she was given hull classification symbol SS-481 on 15 August 1959, and rejoined SubRon 6 in Norfolk for operations as a normal attack submarine, a role she retained until her decommissioning.

Then a helicopter dropped an exercise torpedo on Requin, which hit forward and made several re-attacks bouncing down the port side of the submarine.

Requin's crew prepared to go to the defense of Liberty, but received orders from the Sixth Fleet commander to surface and proceed to Crete.

On 28 May 1968, during her last deployment before decommissioning, Requin departed Norfolk, Virginia, as part of the search effort for the missing nuclear attack submarine Scorpion (SSN-589).