Carlo Cassola was born in Rome on 17 March 1917 into a petit-bourgeois family. He had a secular education and attended public school. His father, a socialist, passed on to him the libertarian tradition; his mother, on the other hand, instilled in him a love for Tuscany, which was a summer holiday destination in his youth. From the mid-1930s onwards, he developed an anti-fascist political consciousness, first by organising a university political protest group, which was soon disbanded, and then by reluctantly undertaking military service. In 1939, he graduated in law, but his real passion was literature: he taught, wrote and collaborated with various magazines.

Starting in 1941, he first joined the liberal-socialist movement, then the Action Party. After the Armistice of Cassibile, he chose to participate in the Resistance against the German occupation and the Italian Social Republic. His activity was recognised from 1 January to 20 July 1944 in the communist-inspired 23rd Garibaldi Brigade Guido Boscaglia. Under the battle name 'Giacomo', he headed the explosives squad, operating in the area between Volterra, the Alta Val di Cecina and the Alto Grossetano. Displaced to Volterra, he contributed to the local section of the National Liberation Committee and supported several local anti-fascist newspapers, devoting himself full-time to political activity.

In 1945 he settled in Florence where he collaborated with various magazines, including La Nazione del Popolo (newspaper of the Tuscan Liberation Committee). The following year he was among the initiators of the appeal 'Italian intellectuals for the Republic' calling for the abolition of the monarchy. In the meantime, he resigned from the Partito d'Azione (Action Party): this marked a sharp departure from political engagement in favour of resuming his literary profession. He recalled the Resistance experience in his novels and short stories, particularly in 'Fausto e Anna', an autobiographical book. The novel 'La ragazza di Bube', published in 1960, won the Strega prize and brought him great notoriety.

In 1974 in Pescia, while attending a conference on Collodi, he met Pola Natali, a local girl, and he moved with her to Montecarlo in the province of Lucca in 1978. Here he died on 29 January 1987. He was buried in the local cemetery; the funeral was held in a strictly private civil ceremony.