The 9th Hussars were mobilized on 2 August 1914, commanded by Colonel Burette. The regiment was positioned between 14th and 21st Corps, fighting in the Battle of the Frontiers. On 19 September, the regiment was transported by rail to the Somme where it faced the 21st Prussian Corps. The 9th Hussars became part of the 1st Cavalry Corps on 21 October and participated in the Race to the Sea. Brought back to Amiens in December, the 9th Hussars were in operations on the Somme until August 1916. On 6 August 1916, the regiment was relocated to take part in the Second Battle of Champagne, as part of 14th Corps. The 9th Hussars attacked on 26 September, suffering heavy losses. After the offensive, the regiment was moved to Montbéliard. In response to the German attacks at Verdun, the regiment was transferred to the Meuse on 29 February 1916. In December 1917, the regiment was moved to the Somme again and left on 28 May for the Chemin des Dames. The regiment took part in the Battle of Malmaison from 16 August to 23 October. In November, the 9th Hussars were withdrawn and stationed in Villiers-Cotterets. In January 1918, the regiment moved to Alsace. As part of 14th Corps, the 9th Hussars retreated to the Somme after the German spring offensive in early April. The regiment participated in the Fifth Battle of Ypres in the last months of the war. The regiment was disbanded in 1922 at Chambéry, where it was then on garrison duties.