Pisacane was born in Naples to an impoverished noble family, and entered the Neapolitan army in 1839; but having become imbued with Mazzinian ideas he emigrated in 1847, and after a short stay in England and France served in the French army in Algeria. The revolution of 1848 recalled him to Italy; he played a part in the brief Roman Republic, and was an instrumental part of the war commission in the defence of the city. After its capture by the French, he again went into exile, first to London and then to Genoa, maintaining himself by teaching. He was an atheist.