Following the end of his partnership with Winchester, Browning sought a new manufacturing partner and entered into a long and fruitful collaboration with Fabrique Nationale (FN) in Herstal, Belgium.

Browning designed the FN Model 1903 pistol, a blowback-operated semi-automatic pistol chambered in 9mm Browning Long (.380 ACP). It was widely adopted by military and police forces worldwide.

Browning designed the FN Model 1906, also known as the Browning Vest Pocket, a small, easily concealable semi-automatic pistol chambered in .25 ACP. It became immensely popular as a civilian self-defense weapon.

Browning designed the Browning Automatic Rifle (BAR), a select-fire, air-cooled, gas-operated automatic rifle. It became a standard light machine gun for the U.S. military in both World War I and World War II and beyond.

Developed earlier, but manufactured extensively by FN, the Auto-5, a recoil-operated semi-automatic shotgun, became a groundbreaking design. It was a commercial success and influenced the development of future autoloading shotguns. It was also produced under license by Remington as the Model 11 and Savage as the Model 720.

Browning's last major design was the Browning Superposed over-and-under shotgun. He considered this his finest achievement, combining elegance, reliability, and superior performance. Production began shortly after his death.