In 1929, the Imperial Japanese Navy Air Service developed a requirement for a large twin-engined carrier-based torpedo-bomber, with an order being placed with Mitsubishi in January 1930.

The remaining five prototypes (3MT5) were completed in 1933 incorporating modifications based on initial testing, with a twin tail replacing the single fin and rudder of the first four aircraft, three-bay wings and four-bladed propellers being fitted.

Despite these changes, the aircraft was difficult to control, and suffered from severe vibration, which on one test flight in March 1934, resulted in all four ailerons being torn off the wings of one of the prototypes, which was safely landed.

These problems could not be resolved, and the lengthy development meant that the type was now obsolete, so no production followed.

[3] The Mitsubishi 3MT5 was variously designated:- Data from Japanese Aircraft 1910–1941[3]General characteristics Performance Armament