Spinelli was born in Rome, and joined the Italian Communist Party (PCI) at an early age in order to oppose the regime of Benito Mussolini's National Fascist Party.
Spinelli syntyi Roomassa, ja liittyi jo nuorena Italian kommunistisen puolueen (PCI) jäseneksi, jotta voisi vastustaa Benito Mussolinin fasistipuoluetta.