The Cougar first entered squadron service in November 1952, when VF-32 converted to the F9F-6. F9F-6s and F9F-7s subsequently re-equipped some twenty Navy fighter squadrons. Eight of these squadrons later converted to the F9F-8.
The Cougar was too late to fly combat sorties in Korea. Immediately following the Korean War, large numbers of Cougars entered service with carrier-based Navy fighter squadrons, and Cougar-equipped squadrons made numerous deployments to the Pacific, Atlantic, and Mediterranean. By the mid-1950s, the Cougar was the most numerous carrier-based fighter serving with the US Navy. The Cougar was popular with its crews, who admired it for its pleasant handling properties and its strong airframe. However, the Cougar was destined to have a short front-line operational life because of the rapid development of more advanced supersonic carrier-based fighters such as the Vought F8U Crusader and the Grumman F11F Tiger. In the late 1950s, the Cougar was replaced in the fighter and reconnaissance roles by the Tiger and the Crusader, and Douglas A4D Skyhawks replaced the Cougar in the light attack role. The last F9F-8 and F9F-8B Cougars were phased out in the Pacific and Atlantic Fleets in 1958 and 1959, respectively. However, some F9F-8Ps were retained by VFP-62 until February 1960.
Following their removal from active-duty fleet squadrons, the Cougars remained with reserve units until the mid-1960s. Surplus Cougars also served as drones and as drone directors. Surviving Cougars were retired to the boneyards at Davis-Monthan AFB in Arizona in the mid to late 1960s.
The Blue Angels flight demonstration team flew F9F-8s from 1954 to 1957, when they converted to the F11F-1 Tiger. The team still retained an F9F-8T until they converted to Phantoms in 1969.
The F9F Cougar served as an advanced jet trainer with VT-21, VT-22, VT-24, and VT-25. The two-place TF-9J and the single-seat TAF-9J wer both used. Many two-seat TF-9s were used by Naval Air Stations as proficiency aircraft for desk-bound aviators in order to earn their required flight time.
The F9F-6 Cougar did not serve with any Marine Corps fleet squadrons, but F9F-6s were assigned to at least twenty Marine Corps reserve squadrons following their phasing out by Navy fleet squadrons. F9F-6Ps served with VMJ-2 at MCAS Cherry Point, North Carolina, and F9F-8Ps served with VMCJ-3 at MCAS El Toro, California. In the late 1950s, F9F-8s and F9F-8Bs were flown by VMCJ-2, VMF-311, VMA-533, and VMFT-10. VMIT-10 used F9F-8Ts as instrument trainers, and Headquarters and Maintenance Squadrons (H&MS-11, -13, -15, and -37) used F9F-8Ts for a variety of duties. In 1966-67, four TF-9Js of H&MS-13 were used in the airborne command role to direct airstrikes against enemy positions in South Vietnam. This marked the only use of the Cougar in combat.
The only foreign air arm to use the Cougar was Argentina's Servicio de Aviacion Naval, which had also used the Cougar's straight-wing predecessor, the F9F-2 Panther. Argentina obtained two ex-Navy F9F-8Ts in 1962. They were assigned the serials 0516 and 0517 and served with the 1a Escuadrilla Aeronaval de Ataque, 3a Escuadra Aeronaval, based at NAN Comandante Espora. They were withdrawn from use in 1971.