In 1937, the Glenn L. Martin Company designed a new twin engined flying boat to succeed its earlier Martin P3M and supplement the Consolidated PBY, the Model 162. It received an order for a single prototype XPBM-1 on 30 June 1937. This was followed by an initial production order for 21 PBM-1 aircraft on 28 December 1937.
To test the PBM's layout, Martin built a three-eighth scale flying model, the Martin 162A Tadpole Clipper with a crew of one and powered by a single 120 hp (90 kW) Chevrolet engine, this flying in December 1937. The first genuine PBM, the XPBM-1, flew on 18 February 1939.