Following two months of shakedown along the Atlantic coast and in the Caribbean, she departed Guantanamo Bay, Cuba, 7 June for a five-week cruise to Northern Europe that carried her to Dutch, German, and Danish ports on the North and Baltic Seas.

[1] On 29 November she entered the New York Shipyard to receive an experimental model of the Variable Depth Sonar (VDS) and thus became the first of the destroyer escorts to employ this latest development in ASW equipment.

Resuming her operations 4 February 1959, she spent the remainder of 1959 and the early part of 1960 testing and evaluating the new equipment and conducting ASW exercises along the Atlantic coast from Newfoundland to Key West.

The destroyer escort returned to the Caribbean on 2 December after participating in the recovery of the Project Mercury MA-5 spacecraft, which on 29 November, twice orbited the Earth with a chimpanzee, Enos, on board.

John Willis sailed to the Dominican Republic on 2 December and commenced seven days of patrol duty after which she returned to Newport to prepare for another cruise to Northern Europe.

While sailing the North Sea on 23 January en route to Horton, Norway, she assisted units of the British Navy during search and rescue operations for stricken Norwegian ship, Eystein.

While engaging in maneuvers designed to detect and destroy nuclear submarines, John Willis provided search and rescue assistance 23 September for a MATS plane, which was lost in the North Atlantic on a flight from Dover, Delaware, to the Azores.

For the next three years John Willis continued to operate along the Atlantic Coast and in the Caribbean while taking part in squadron exercises and serving as school ship at Key West.

Between January and June 1966 she underwent extensive overhaul at Boston, Massachusetts where she received DASH capabilities and communications alterations: thence she resumed refresher and readiness training out of Newport.