The CAMS 31 was a wooden-built two-bay equal span biplane with stabilising floats under each wing and an open cockpit forward of the lower-wing for the pilot. Powered by a Hispano-Suiza 8Fb inline piston engine driving a pusher propeller, the engine was strut mounted between the wings. The CAMS 31 was armed with two fixed hull-mounted Vickers machine-guns in the bow.
The CAMS 31 prototype, later designated the CAMS 31 Type 22, first flew in 1922. A second prototype, the CAMS 31 Type 23, flew in 1923 with a reduced-span wing and wider chord but still had the same wing area as the Type 22. Testing proved the flying-boats handled well but were just not suitable as fighters and no more were built.
A mail carrying postal variant was designated CAMS 31P