Son of Bennone, archivist in the Austrian administration, and Teresa Rigo, he was the last of four brothers (preceded by Ada, Nilo and Adone).

Subsequently, he enrolled at the Ca' Foscari University of Venice where he graduated in Foreign Languages and Literatures, presenting a thesis on Baudelaire's poetics.

He was engaged in France, Albania, Montenegro, the Dauphiné; after 8 September 1943 he was taken prisoner and managed to escape from the German convoy which was to lead him to a concentration camp in Poland.

During this mandate Piccoli, together with Monsignor Alfonso Cesconi, claims the need for distinction between the religious and spiritual formation tasks of Catholic associations and the political and autonomous role of the party.

On 19 January 1969, Piccoli was elected national secretary of the party, a position he voluntarily left in the autumn of the same year following the division of the Dorotean faction into the factions "Popular Initiative" (the majority area that referred to Piccoli, Rumor and Bisaglia) and "Democratic Commitment" (which instead brought together the exponents who recognize themselves in Emilio Colombo and Giulio Andreotti).

After the 1982 Congress in Rome, which elected Ciriaco De Mita as political secretary, he was again called to the presidency of the National Council, a position held until May 1986.

As president of the Foreign Commission, in April 1988 he made a trip to the Soviet Union, during which he pronounced some phrases related to the Italian expedition to Russia in the Second World War that aroused controversial reactions (especially by MP Mirko Tremaglia of the Italian Social Movement, also a member of the commission) and a debate in the Chamber.