Following World War II, the Yorktown missed Korea due to being in a yard period, but participated in peacekeeping exercises off Taiwan in the mid-1950s. She underwent conversion to SCB-27 standard, receiving an angle deck and various other refinements now commonplace on modern supercarriers. In 1957, her designation was changed from an attack carrier (CVA) to an antisubmarine warfare carrier (CVS). Officially, her role was "Surface and Subsurface Search and Coordination," or SSSC. It was in this role that she participated in four war cruises off Vietnam (three "official" cruises, plus one "Magic Carpet" aircraft ferrying cruise). The Yorktown's job was to assist in Operation Market Time, keeping track of all shipping in the Tonkin Gulf area, but primarily it participated in search and rescue operations of pilots downed in the Gulf after airstrikes on Vietnam. For these purposes, the Yorktown embarked three types of aircraft: the Grumman S-2 Tracker antisubmarine/search aircraft, the Grumman E-1 Tracer airborne early warning aircraft, and the Sikorsky SH-3 Sea King antisubmarine/rescue helicopter. Since the Yorktown was a CVS, she retained older hydraulic catapults instead of steam catapults, which rendered her unable to launch jet aircraft, except the small A-4 Skyhawk attack aircraft, which were occasionally carried.

Official U.S. Navy photo from the estate of W.P. Tyler, CO of USS Hopewell at the time.