After law studies at the University of Trieste, Vidussoni joined the Partito Nazionale Fascista (PNF) in May 1936. He was a volunteer soldier in the Second Italo-Abyssinian War, and then on Francisco Franco's side in the Spanish Civil War; he lost an eye and an arm on the Santander front, and was awarded a gold medal for valor in combat. Aldo Vidussoni's reputation made him an asset with the Benito Mussolini régime, and he became an important figure in the hierarchy of the Fascist university corporations - the Gruppi universitari fascisti (GUF). First a secretary of the GUF for the Province of Trieste (in 1938), he was (1940-1941) inspector for the GUF in Enna, and, in November-December 1941, national secretary of the GUF.
On December 26, still quite young, Vidussoni was appointed national secretary of the PNF (replacing Adelchi Serena, by order of Mussolini). His scarce political experience and the constant criticism of other leaders had made him ill-suited for the task, and he was suddenly replaced by Carlo Scorza in April 1943.
After the pro-Allied coup inside the Grand Council of Fascism in late July 1943 and the armistice signed by the Pietro Badoglio government in Cassibile, Vidussoni chose to side with the Nazi-backed Italian Social Republic (established and led by Mussolini in the north). He became a leading member of the refounded PNF, the Partito Fascista Repubblicano (Republican Fascist Party).