Designed as a dual purpose weapon for use against both aircraft and ground targets, it was effective against light tanks, with the armour piercing round being able to penetrate 30 millimeters of armour at a range of 500 meters. It had a two-wheeled trailer, but due to its structural weakness that limited the towing speed to 20 km/h, the weapon was usually transported on a truck bed instead.
The Model 35 was used also in vehicle mounting, initially in four Panzer Is converted during the Spanish Civil War, by the Nationalists, in an effort to improve their fighting capability against the Soviet T-26s fielded by the Republican forces. Later the gun was fitted to Fiat L6/40 light tanks and the AB 41 armoured cars and in addition, it was employed as a deck-mounted anti-aircraft weapon in at least in some of the MAS torpedo boats. The naval mounting had an elevation of -10 to +90 degrees and it used the same sights as the land based version.
After the Winter War had begun, Finland bought a total of 88 Breda guns from Italy, last ones arriving during the Interim Peace in June 1940. Five of the Finnish Bredas were later lost in action during the Continuation War. In addition, the four Italian-built Jymy class motor torpedo boats operated by the Finnish Navy each had one 20 mm Breda cannon on the rear deck.
In North Africa, the Commonwealth forces captured a large number of Breda Model 35s during the Operation Compass, enabling the Australian 2/3 Light Anti-Aircraft Regiment, parts of the 4th Anti-Aircraft Brigade (which had a total of 42 Bredas in its Light Anti-Aircraft batteries during the Siege of Tobruk) and one battery of 106 RHA, the Lancashire Hussars Yeomanry to be equipped with them. In addition, captured guns were employed aboard a number of Royal Australian Navy and Royal Navy vessels including HMAS Vendetta, HMAS Perth and HMS Ladybird, and at least on one Marmon-Herrington Mk II armoured car .
The Finnish Defence Forces used the 20 ItK/35 Breda, as the gun was officially known in that service, as a training weapon for anti-aircraft crews for several decades after the end of World War II. In 1985 there were still 76 guns remaining in the inventory, but all of those were discarded later during that decade.