The pistol was developed in the late 1950s at the Institute for Artillery Research (Polish: Zakład Broni Strzeleckiej Centralnego Badawczego Poligonu Artyleryjskiego, which later became the Military Institute of Armament Technology, Polish: Wojskowy Instytut Techniczny Uzbrojenia w Zielonce—WITU) by a team consisting of: W. Czepukajtis, R. Zimny, H. Adamczyk, M. Adamczyk, S. Kaczmarski and J. Pyzel.

In 1965, the P-64, manufactured at the Łucznik Arms Factory in Radom, entered service with the army, police and security forces under the official designation 9 mm pistolet wz.

The rotating slide catch, installed inside the pistol's frame, contains a protrusion which acts as an empty case ejector.

In the "safe" position, the firing pin is locked and the trigger bar is disconnected from the hammer notch.

In 1971 the hammer was modified internally, although some 1971 dated examples exist without the modification, those can be distinguished by the absence of an "A" marking on the receiver, behind the grip.

In 1973 the trigger mechanism was modified and the hammer was changed to a triangular shape, designed to be easier for cocking with the thumb.

In 1972, a prototype pistol was developed (called the P-70) with a 14-round magazine capacity and a slide made from copper-welded stamped steel.

Production of the P-78 was terminated after it lost out to the P-83 Wanad pistol in a bid for a new service sidearm for the Polish Army and police.