His father was a descendant of the Counts of Castel San Giovanni, an illegitimate branch of the House of Sforza who had ruled the Duchy of Milan in the fifteenth and sixteenth centuries.

Visconti-Venosta's recommendation earned him the post of first secretary of legation in Madrid (1906-1907), before being sent as chargé d'affaires in Constantinople (1908-1909) where he witnessed the Young Turk Revolution.

In 1921 Sforza upset nationalist right-wing forces by signing the Rapallo Treaty which recognised the important port of Fiume as a free city.

Sforza was appointed ambassador to France in February 1922 but resigned from office nine months later on 31 October after Benito Mussolini had gained power.

While living in exile in Belgium, the native country of his wife, Sforza published the books, European Dictatorships, Contemporary Italy, Synthesis of Europe, as well as many articles where he analysed the fascist ideology and attacked its many well-wishers as well as different "appeasers" in England, France and elsewhere.

Attending the Italian-American Congress in Montevideo, Uruguay, in August 1942, he presented an eight-point agenda for the establishment of an Italian liberal democratic republic within the Atlantic Charter.

On 4 March 1911 in Vienna, Sforza married a Belgian aristocrat, Countess Valentine Errembault de Dudzeele et d'Orroir (Bern 4 March 1875 – Rome, 31 January 1969), whose father, Count Gaston (1847-1929), was Belgian ambassador to Constantinople and later to Vienna, and whose brother, Count Gaston Errembault de Dudzeele, would marry in 1920 the widow of Prince Mirko of Montenegro, himself a brother-in-law of the King of Italy.

[4] Sforza and his wife had a daughter, Fiammetta (Beijing 3 October 1914 – 2002), who married Howard Scott ("a divorced father-of-two non-Catholic and penniless Englishman"), and a son, Count Sforza-Galeazzo («Sforzino») Sforza (Corfu 6 September 1916 – Strasbourg 28 December 1977), a sculptor, for a time the lover of Argentine painter Leonor Fini, and later Deputy Secretary General of the Council of Europe (1968-1978).