The TB was an improved version of the Martin T3M. It was constructed of all dural, with a fabric covering. The equal-span wings were large and unstaggered, and could be folded aft, reducing the span to 21 feet 8 inches (6.60 m) for storage. The wheeled undercarriage was a conventional configuration that could be interchanged with floats. As a landplane, the main gear units carried twin wheels. The underside of the fuselage incorporated a glazed station for the bombardier.
Even before the three XTB-1s were delivered, the Navy's Bureau of Aeronautics had changed its opinion about what was needed in a torpedo bomber, and based on experience with the NAF XTN-1 had decided that a twin-engine aircraft would better suit the role. Having thus been made redundant, no TBs past the three prototypes were built.