Cornelia married Tiberius Sempronius Gracchus when he was already in an advanced age. The union proved to be a happy one and together they had twelve children, very unusual for Roman standards. From these only three survived childhood: Sempronia, married to her cousin Scipio Aemillianus, and the brothers Tiberius and Gaius Gracchus, who would defy the political institutions of Rome, with their attempts of popular reforms. After her husband's death, she chose to remain a widow, even when the pretender was king Ptomoly VIII of Egypt, and set herself to educate her children. Cornelia always supported Tiberius and Gaius, even when their actions outraged the conservative patrician families in which she was born. After their violent death she retired Rome to a villa in Misenum, but continued to receive guests.
Rome worshiped her immaculate virtues and when she died at an advanced age, the city voted for a statue in her honour: the first attributed to a non-mythological woman.