Breaking the oath he had sworn to Sulla that he would not attempt any revolution in the state, Cinna allied himself with Marius, raised an army of Italians, and took possession of the city. Soon after his triumphant entry and the massacre of the friends of Sulla, by which he had satisfied his vengeance, Marius died. Lucius Valerius Flaccus became Cinna's colleague, and on the murder of Flaccus, Cn. Papirius Carbo. In 84, however, Cinna, who was still consul, was forced to advance against Sulla; but while embarking his troops to meet him in Thessaly, he was killed in a mutiny.
His daughter Cornelia was the wife of Julius Caesar, the dictator; but his son, L. Cornelius Cinna, praetor ill 44 BC, nevertheless sided with the murderers of Caesar and publicly extolled their action.
The hero of Pierre Corneille's tragedy Cinna (1640) was Cn. Cornelius Cinna, surnamed Magnus (after his maternal grandfather Pompey), who was magnanimously pardoned by Augustus for conspiring against him.