At the outbreak of World War I in August 1914, she participated in the hunt for the German battlecruiser SMS Goeben and then joined the blockade of the Austro-Hungarian Navy in the Adriatic.

Ernest Renan was intended to be a member of the Leon Gambetta class, but naval architect Emile Bertin repeatedly tinkered with the design and decided to lengthen the ship in an attempt to increase her speed.

A watertight internal cofferdam, filled with cellulose, ran the length of the ship between the upper and main decks.

[3][Note 2] During the launch, general manager of Schneider-Creusot Maurice Geny died in a falling incident.

[2] After entering service, Ernest Renan was assigned to the cruiser squadron of the Mediterranean Fleet, based in Toulon.

[6] At the outbreak of World War I in August 1914, Ernest Renan and the armored cruisers Edgar Quinet and Jules Michelet were mobilized as the First Light Division and tasked with hunting down the German battlecruiser SMS Goeben and the light cruiser SMS Breslau.

The fleet, commanded by Admiral Augustin Boué de Lapeyrère, had assembled by the night of 15 August; the following morning, it conducted a sweep into the Adriatic and encountered the Austro-Hungarian cruiser SMS Zenta.

[9] On 8 January 1916, Ernest Renan, Edgar Quinet, Waldeck-Rousseau and Jules Ferry embarked a contingent of Chasseurs Alpins (mountain troops) to seize the Greek island of Corfu.

The cruisers sent the troops ashore on the night of 10 January; the Greek officials on the island protested the move but offered no resistance.

Ernest Renan was among the first Allied warships to enter the area; she arrived in Novorossiysk with the British light cruiser HMS Liverpool and two torpedo boats on 23 November 1918.

[7] Ernest Renan finished her active career as a gunnery training ship from 1927 to 1929, after which she was stricken from the naval register.