It originally manufactured locomotives and other railway machinery, but later branched out into armaments and aircraft.

Breda-designed machine guns such as the Breda Model 30 and Breda Model 37 were standard issue weapons for the Royal Italian Army during the Second Italo-Abyssinian War, the Italian Invasion of Albania and World War 2.

The train and tram manufacturing division fused with Ansaldo to form AnsaldoBreda, the armaments division became an independent entity as Breda Meccanica Bresciana, as did the research division as Istituto Scientifico Breda.

Between 1936 and 1940, the company built a total of 28 trolleybuses, most for the Rome system but including six for Genoa.

Almost all of Breda's customers for trolleybuses were Italian trolleybus systems, but a notable exception was an order of 236 dual-mode buses that Breda built for the Seattle system between 1988 and 1991.