Born in Sassari, in his youth he was a follower of the Meridionalist activist Gaetano Salvemini. After his graduation in law he collaborated with the newspaper La Nuova Sardegna and other Italian newspapers.
In 1921 he abandoned the Italian Socialist Party (PSI) and adhered to the Italian Communist Party (PCI), with which he was elected in the Italian Chamber of Deputies in 1924. The following year he founded the clandestine newspaper Sardegna libera ("Free Sardinia") which attracted him the hostility of the Fascist regime. A friend of Palmiro Togliatti, after the armistice with Italy (September 1943), he left the PCI and entered the Sardinian Action Party. For the latter Berlinguer was a member of the second government formed by Pietro Badoglio in southern Italy.
In 1945 he was named to the National Consult and collaborated to the elaboration of the special regional status for Sardinia. He was a deputy for PSI from 1948 to 1953.