He was educated at the Lyceé Bonaparte.
He served on General Chanzy’s staff during the war of 1870 and was taken prisoner at Le Mans, but after the war entered the public service. After a short period at the Ministry of Public Instruction, he entered the diplomatic service, and was appointed first secretary at Washington, District of Columbia In 1882 he returned to France and took up journalism. He was a contributor to many journals, including the Revue des Deux Mondes and the République Française, and in 1888 became foreign editor of the Temps.
On the rise of the Dreyfus Affair (1895) de Pressensé identified himself with the cause of the prisoner.
He was prominent in the debates on the question of the separation of church and state, and a bill brought in by him formed the basis of the one finally carried by Aristide Briand.
This led to his resignation from the Temps, and he came forward as a socialist politician, being in 1902 elected socialist deputy for the Rhône.
Human Rights League.