The squadron was administratively transferred to Marine Aircraft Group 12 in October 1950. MGCIS-1 secured operations in Hungnam on 11 December and all personnel boarded an LST on December 13 as part of the Hungnam evacuation. While afloat, squadron controllers assisted their US Navy counterparts controlling hundreds of aircraft daily during the operation. The squadron sailed for Pusan, Korea and set up its equipment at Pusan West AB (K-1) as it prepared for follow-on tasking. In April 1951 MGCIS-1 was again administratively transferred to under the control of MACG-2. MGCIS-1 participated in the defense of the Korean Demilitarized Zone from July 1953 through March 1955. On February 15, 1954 the squadron received its current moniker of Marine Air Control Squadron 1.. In April 1955 the unit redeployed to Naval Air Facility Atsugi, Japan, and was reassigned to Marine Aircraft Group 11 (MAG-11).