Cassard was briefly deployed to search for German commerce raiders and blockade runners in late 1939 and early 1940, but returned to the Mediterranean in time to participate in Operation Vado, a bombardment of Italian coastal facilities after Italy entered the war in June.

The turbines were designed to produce 64,000 metric horsepower (47,000 kW; 63,000 shp), which would propel the ships at 36 knots (67 km/h; 41 mph).

During her sea trials on 26 August 1932, Cassard's turbines provided 76,833 PS (56,511 kW; 75,782 shp) and she reached 41 knots (76 km/h; 47 mph) for a single hour.

The ships carried enough fuel oil to give them a range of 3,000 nautical miles (5,600 km; 3,500 mi) at 14 knots (26 km/h; 16 mph).

They were also fitted with a pair of depth-charge throwers, one on each broadside abreast the aft funnels, for which they carried a dozen 100-kilogram (220 lb) depth charges.

The Navy reconsidered its anti-submarine warfare tactics after the war began in September and intended to reinstate the depth-charge throwers, although these were an older model than the one previously installed; Cassard received hers in May 1940 at Toulon.

After the start of the Spanish Civil War in July 1936, the contre-torpilleurs and destroyers in the Mediterranean were assigned to assist French citizens in Spain and to patrol the surveillance zones assigned to France on a monthly rotation beginning on 24 September as part of the non-intervention agreement.

The 9th DL participated in a naval review held by the Navy Minister Alphonse Gasnier-Duparc in Brest on 27 May 1937.

The 9th Scout Division with Cassard, Kersaint and Maillé Brézé was assigned to escort duties until April 1940, although the former ship was detached (12 November–21 January 1940) to Force X in the Atlantic which was tasked to search for German commerce raiders and blockade runners.

The Vichy French reformed the FHM on 25 September after it negotiated rules limiting the force's activities and numbers with the Italian and German Armistice Commissions.

Cassard was the only ship of her class assigned to it and was one of its escorts when they made a training sortie into the Western Mediterranean on 16–18 October.