 At the beginning of the war, the ship, together with her sister Condorcet and the dreadnought Courbet, unsuccessfully searched for the German battlecruiser Goeben and the light cruiser Breslau in the Balearic Islands. She later escorted troop convoys from North Africa to France before she joined her sisters at Malta. On 16 August 1914 the combined Anglo-French Fleet under Admiral Auguste Boué de Lapeyrère, including Vergniaud, made a sweep of the Adriatic Sea. The Allied ships encountered the Austro-Hungarian cruiser SMS Zenta, escorted by the destroyer SMS Ulan, blockading the coast of Montenegro. There were too many ships for Zenta to escape, so she remained behind to allow Ulan to get away and was sunk by gunfire during the Battle of Antivari off the coast of Bar, Montenegro. Vergniaud was one of the ships that bombarded Cattaro on 1 September and blockaded the Strait of Otranto for the rest of the year and through August 1915. She was based at Malta and Bizerte until February 1916 when she sailed to Toulon.
