Antonio joined the Communist Party in 1940 and was arrested and tried, but acquitted, for his associations with them.
In the spring of 1943 Giolitti resumed his clandestine activities, for the Communist Party, contacting numerous military and political personalities, in order plan the overthrow of the fascist regime. During the Second World War, Giolitti was seriously wounded in combat. He was sent to France to recover, and was not able to return to Italy until after the war ended.
After the war, Giolitti was involved in much political activity: He was undersecretary to the Foreign minister for Parri's government, communist deputy to the Constituent Assembly, elected to the Chamber of Deputies in the list of the PCI in 1948 and 1953. In 1957 he left the Communist Party and joined the PSI.
Antonio Giolitti was a deputy minister until 1985. He served as budget minister in the first Moro government; he has been also minister of the Budget in the first Moor government. For four years, he was a member of the Executive Commission of the European Economic Community in Brussels.
In 1987, Giolitti returned to the PCI and was elected senator. At the end of his legislative period, he withdrew himself from active politics.
Antonio Giolitti has written important political texts and, in 1992, he published his memoirs.
In 2006 he was awarded Cavaliere di Gran Croce, the highest from the President of the Italian Republic.