This variant was widely used by the Royal Italian Army on all theatres of World War II Italy was involved in.

It is widely acknowledged as the most successful and effective Italian small arm of World War II and was produced in large numbers in several variants.

[6] Italy's limited industrial base in World War II was no real barrier toward the development of advanced and effective small arms since most weapons of the time required large amounts of artisan and semi-artisan man-hours to be fine-tuned anyway.

The MAB 38 was developed by Beretta to compete in the sub-machine gun market; it was a well-made and sturdy weapon, introduced several advanced features, and was suitable for police and special army units.

Army orders were slow to come; although impressed by the excellent qualities and firepower of the weapon, the Italian military did not feel the MAB was suitable for standard infantry combat.

A magazine-carrying vest was designed for elite troops (Blackshirts, paratroopers) armed with the Beretta 38; these were dubbed "Samurai" due to the similarity of the stacked magazines to the feudal Japanese warriors' body armour.

The 1938 series was extremely robust and proved very popular with Axis forces as well as Allied troops, who used captured examples.

[11] Firing a more powerful Italian version of the widely distributed 9×19mm Parabellum cartridge, the Cartuccia 9 mm M38, the Beretta was accurate at longer ranges than most other submachine guns.

[7] The MAB could deliver impressive firepower at close range, and at longer distances its size and weight was an advantage, making the weapon stable and easy to control.

MAB 38, in its first variants, was a fine weapon by any standard, crafted with high-quality materials, flawlessly finished, and with carefully machined parts.

The MAB 38 had a wooden stock, was about 800 mm (31 in) long and weighed about 5 kg (11 lb) when loaded, with an effective range of about 200 m (220 yd).

The Model 1938 can be recognized by its machined steel receiver, fine craftsmanship, and finish, and by the perforated cooling jacket over the barrel.

In compliance with Italian army requirements, the bayonet mount and rest were eliminated and the recoil compensator was redesigned, the two horizontal muzzle slots substituted by 4 transversal cuttings, judged more effective.

[17][18][19] The Model 5 was produced for the Italian Army, police and the armed forces of several other nations until 1961 when production ceased in favor of the compact, modern Beretta M12.