Representing the last of the fighter aircraft to be evolved from the M.B.150, which had declined to become airborne in 1936, the Bloch M.B.157 resulted from an attempt to unite the airframe of the M.B.152 with a new and far more powerful Gnome-Rhone 14R, an air-cooled radial engine similar to those which powered the earlier Bloch fighters, but with a power output of 1186kW for take-off, and having a supercharger that could provide a rating of 1268kW at 8000m.

Such power suggested exciting possibilities for a high-altitude interceptor, but the increased size and weight of this engine brought realisation that it would not be practical to install it in the existing M.B.152 airframe. The conclusion that the full potential of the Gnome-Rhone 14R would be lost by attempting an adaptation of the airframe led to a decision to design a new fighter which would retain the same basic structural techniques.

Having postulated such a design philosophy, it was possible to formulate the details of the M.B.157 very rapidly, for the basic design already existed. The result of this was that within just over six months of design initiation, the components of the prototype were ready for assembly but, once again, it was too late for France. With German forces closing in on Paris, the M.B.157 components were loaded to be taken to a place of security but, en route, this vehicle was intercepted by the Germans and ordered to proceed to an SNCASO establishment within the occupied zone.

Finally, in 1942, the M.B.157 was assembled and test flown under German supervision, demonstrating superb performance before being flown to Orly where the powerplant was removed for wind-tunnel testing. This was the most interesting feature so far as the Germans were concerned, and after tests had been completed the engine was transported to Germany. SNCASO's air-frame, which had demonstrated in conjunction with Gnome-Rhone 14R a degree of performance that was not to be attained elsewhere until later in the war, was destroyed during an Allied air raid.