In 1935, the U.S. Navy issued a requirement for a carrier-based fighter intended to replace the Grumman F3F biplane. The Brewster XF2A-1 monoplane, designed by a team led by Dayton T. Brown, was one of two aircraft designs that were initially considered. The XF4F-1 with a double-row radial engine was a "classic" biplane. The U.S. Navy competition was re-opened to allow another competitor, the XFNF-1, a navalized Seversky P-35 eliminated early on when the prototype could not reach more than 267 mph (430 km/h). The XF2A-1 first flew on 2 December 1937 and early test results showed it was far in advance of the Grumman biplane entry. While the XF4F-1 would not enter production, it would later re-emerge as a monoplane, the Wildcat.
The new Brewster fighter had a modern look with a stubby fuselage, mid-set monoplane wings and a host of advanced features. It was all-metal, with flush-riveted, stressed aluminum construction, although control surfaces were still fabric-covered. The XF2A-1 also featured split flaps, a hydraulically operated retractable main undercarriage (and partially retractable tailwheel), and a streamlined framed canopy. However (as was still common at this time), the aircraft lacked self-sealing fuel tanks and pilot armor. Fuel was only 160 U.S. gal (606 l), stored in the fuselage. Powered by a 950 hp (708 kW) single-row Wright R-1820-22 Cyclone radial engine, it had an impressive initial climb rate of 2,750 ft/min and a top speed of 277.5 mph (447 km/h), later boosted to 304 mph (489 km/h) at 16,000 ft (4,879 m) after improvements were made to the cowling streamlining and carburetor/oil cooler intakes. With only a single-stage supercharger, high-altitude performance fell off rapidly. Fuselage armament was one fixed .50 in (12.7 mm) M2 Browning machine gun with 200 rounds and one fixed .30 in (7.62 mm) AN Browning machine gun with 600 rounds, both in the nose. The Navy awarded Brewster Aeronautical Corporation a production contract for 54 aircraft as the F2A-1.
Service testing of the XF2A-1 prototype began in January 1938 and in June, production started on the F2A-1. They were powered by the 940 hp (701 kW) Wright R-1820-34 engine and had a larger fin. The added weight of two additional .50 in (12.7 mm) Browning wing guns and other equipment specified by the Navy for combat operations reduced the initial rate of climb to 2,600 ft/min. Plagued by production difficulties, Brewster delivered only 11 F2A-1 aircraft to the Navy; the remainder of the order was later diverted to the Finnish Air Force in modified form under the export designation Model 239.
A later variant, the F2A-2, of which 43 were ordered by the U.S. Navy, included a more powerful R-1820-40 engine, a better propeller, and integral flotation gear, but still lacked pilot armor and self-sealing tanks. The increase in engine power was welcomed, but to some extent offset by the increased loaded weight (5,942 lb/2,701 kg) of the aircraft; while top speed was increased to a respectable 323 mph (520 km/h) at 16,500 ft (5,029 m), initial climb rate dropped to 2,500 ft/min. Both the F2A-1 and the F2A-2 variants of the Brewster were liked by early Navy and Marine pilots, including Pappy Boyington, who praised the good turning and maneuvering abilities of the aircraft. Boyington observed: "But the early models, before they weighed it all down with armor plate, radios, and other [equipment], they were pretty sweet little ships. Not real fast, but the little [aircraft] could turn and roll in a phone booth." This might be expected from the low wing loading, only 24.1 pounds per square foot, only 10% higher than that of the Zero.
The F2A-3 was the last version of the Buffalo to enter service with the U.S. Navy and Marine Corps. A total of 108 examples were ordered in January 1941. By this time, the Navy had become disenchanted with the Buffalo, and had become especially annoyed at Brewster Aeronautical Corporation's frequent production delays and its seemingly never-ending management difficulties. This order was seen more as a way of keeping Brewster's production lines running; they would eventually build Corsair fighters for the Navy as well as Buccaneer/Bermuda dive bombers.
The F2A-3s were conceived as a long range reconnaissance fighter with a new wet wing with self-sealing features and a larger fuselage tank which provided increased fuel capacity and protection, but this also increased the aircraft's weight by more than 500 lb (227 kg). The wing and enlarged fuselage tank carried an additional 80 U.S. gal (300 L) of fuel; at 6 lb/U.S. gal (0.72 kg/L), the fuel alone weighed nearly 500 lb (227 kg). The addition of armor plating for the pilot and increased ammunition capacity further increased the aircraft's weight, resulting in a reduced top speed and rate of climb, while substantially degrading the Brewster's turning and maneuvering capability. The Navy found that the added weight of the F2A-3 also aggravated the problem of landing gear failure during carrier landings. However, the -40 two speed supercharged Cyclone engine in the F2A-3 was an excellent "cruising" engine and as such the F2A-3 had some value and saw initial service on the carriers Saratoga and Lexington.
Even in late 1940 it was apparent that the Buffalo was rapidly becoming obsolete. It badly needed a more powerful engine, but the limits of the airframe had been reached, making installation of a larger engine impossible. Soon after deliveries of the F2A-3 began, the Navy decided to eliminate the type altogether. By then, considered a second line aircraft, some were transferred to the U.S. Marine Corps, which deployed two F2A-3 squadrons to the Pacific, one at Palmyra Atoll, and another at Midway Island. Those which still remained on board aircraft carriers narrowly missed a combat opportunity when a relief mission was dispatched to Wake Island, but the relief force was withdrawn before completing the mission. Shortly thereafter, F2A-3s still in naval service were transferred to training squadrons for use as advanced trainers.