Jung was an important player in international finance during the interwar period, leading Italian negotiations with the United States over tariff questions, heading Italo-German economic talks with Hermann Göring, and representing Italy at the London Economic Conference during which he was heralded in press reports for his diplomatic tact.

As Italy's alliance with Germany grew stronger, Jung was ultimately sidelined by Mussolini due to his Jewish heritage, despite reports from the Organization for Vigilance and Repression of Anti-Fascism that described him as a disciplined and loyal fascist.

After the surrender of Italy, Jung briefly served as finance minister a second time – in 1944 – under Pietro Badoglio but was dismissed after three months following allegations concerning the extent and depth of his roots in the National Fascist Party.

Though a fanatical fascist, Jung drew a sharp distinction between fascism and Nazism, once comparing the Nazi Party to a baby and later reportedly calling Adolf Hitler a "blockhead".

[3] He also served on the board of directors of the Bank of Palermo, in recognition of which he was, in 1906, invested into the Order of the Crown of Italy at the degree of Cavaliere.

[1][8] During an official visit by Hermann Göring to Italy, Mussolini assigned Jung to meet with the German minister, prompting David Schwartz of the Wisconsin Jewish Chronicle to write that "it must have been a lesson in tolerance".

Soong, that concluded the long-lasting negotiations for the settlement of the Boxer Indemnity and the outstanding amount of the Skoda loan with Italy.

[14] In a 1933 interview with the Jewish Telegraphic Agency, Jung compared Nazism to Fascism by equating it to the difference between "an infant to a ten-year-old boy".