Born in Portici, near Naples, Ferrero studied law in Pisa, Bologna and Turin. Soon afterward he married to Gina Lombroso, a daughter of Cesare Lombroso, a sociologist and historian, with whom he wrote Criminal Woman, the Prostitute and the Normal Woman. In 1891-1894 Ferrero traveled extensively in Europe and in 1897 wrote The Young Europe. After studying the history of Rome Ferrero turned to political essays and novels (Between Two Worlds in 1913, Speeches to the Deaf in 1925 and The Two Truths in 1933-1939). When the fascist reign of Black Shirts forced liberal intellectuals to leave Italy in 1925, Ferrero refused and was placed under house arrest. In 1929 Ferrero accepted a professorship at Geneva. His last works however (Adventure, The Reconstruction of Europe, Power and The Two French Revolutions) were dedicated to the French Revolution and Napoleon.
Ferrero was invited to the White House by Theodore Roosevelt in 1908. He gave lectures in the northeast of the USA which were collected and published in 1909 as Characters and Events of Roman History.