Piccioni was born on 14 July 1892 in Poggio Bustone (Province of Rieti, Umbria) and graduated in Law at the Sapienza University of Rome.

With the advent of fascism in power, in 1926, after the forced dissolution of the PPI, he moved to Pistoia, where he resumed practicing as a lawyer and became a widower.

After the end of the Second World War he moved to Rome and on 2 June 1946 he was elected to the Constituent Assembly among the ranks of the Christian Democrats (DC).

Piccioni, however, did not want to take on this responsibility for the involvement of his son Piero, composer, in the case of Wilma Montesi, a Roman girl found dead on the beach of Torvaianica; thus he was confirmed as Minister of Foreign Affairs in the new Scelba Government.

Two days later, his son Piero was arrested on charges of manslaughter and drug use and then imprisoned in the Regina Coeli prison.