The SEV-3 was an all-metal cantilever low-wing monoplane powered by a nose-mounted 420 hp (313 kW) Wright J-6 Whirlwind radial engine. It had two cockpits in tandem, forward for the pilot and the rear cockpit for two passengers, both with a sliding canopies. It could either be fitted with twin amphibious floats which had main wheels fitted in the floats to allow it to operate from land or with a fixed tailwheel undercarriage with the mainwheels enclosed in large fairings.
The SEV-3 first flew as a floatplane in June 1933 demonstrating excellent performance as both an amphibian and a landplane. It was built in small numbers mainly for export.
Alexander de Seversky standing before the SEV-3XAR, autumn 1934
An SEV-3 established a world speed record for a piston-engined amphibians in 1933 and on 15 September 1935 a Wright Cyclone powered SEV-3 set a record of 230 mph (370.8 km/h) which stood for 49 years. A landplane version was also developed with a conventional landing gear.
The design influenced a long-line of Seversky then Republic aircraft leading to the P-47 Thunderbolt. A landplane version was used by the United States Army Air Corps as a basic trainer with the designation BT-8.