[1][2] De Berti was born in Pago, Austria-Hungary, which is in the present-day Croatia, into an Italian family of Lombard descent.

He founded the daily L'Azione in Pola after the city passed to Italy in 1919, the Camera del lavoro italiana, and Istria's section of the Italian Reformist Socialist Party.

He made a last political attempt with the newspaper L'Arena di Pola (June–September 1925), confident in a "constitutional turn of events supported by the king".

[1] After the fall of Fascism, Bonomi of the Labour Democratic Party invited De Berti to Rome to resume his political activity in parliament; he chose to be appointed temporary prefectural commissioner for the commune of Pola.

[1] During this time, he kept in touch with Trieste's National Liberation Committee but firmly opposed collaboration with the Yugoslavs due to their wish of annexing Istria and Dalmatia.

[1] In 1945, De Berti founded the Comitato Giuliano in Rome, and pressed for the re-foundation of the newspaper L'Arena di Pola.

[1][4] He was with Alcide De Gasperi at the 1945 Council of Foreign Ministers in London and at the 1947 Paris Peace Conference as an expert of the irredent lands.