In the Cavalry, the main user at first, the Hotchkiss tanks replaced as main combat tanks the light AMR 33 and AMR 35 vehicles, that for want of a better type had been used to form the bulk of the first two Cavalry armoured divisions. As the new medium SOMUA S35 was initially produced in very limited numbers, until early 1939 the Hotchkiss equipped three of the four divisional tank regiments.
In April 1940 the 342e CACC was sent to Norway after the German invasion of that country, having first been intended to form part of an expeditionary force to assist Finland in the Winter War. This autonomous company, equipped with fifteen "H 39"s, all with short guns, fought at Narvik, after having landed on 7 May. After the temporary liberation of that city, the twelve remaining vehicles were withdrawn to Britain on 8 June, where they exceptionally joined the Free French, forming the 1e Compagnie de Chars de Combat de la France Libre. In 1940 and 1941 this 1e CCC fought against Vichy troops in the Battle of Gabon and later in Syria.
According to the acceptance lists, when World War II started 640 Hotchkiss tanks had been delivered. The inventories deviate slightly: of the 300 "H 35"s allocated to the Cavalry, 232 were fielded by ten cavalry squadrons, 44 were in depot, eight in factory overhaul and sixteen in North Africa. Of the hundred used by the Infantry, ninety were fielded by the two tank battalions equipped with the type, six were in matériel reserve and two used for driving training. Of the "H 39"s, sixteen were used by the Cavalry in North Africa and six in depot; 180 were fielded by four Infantry tank battalions and fourteen were in the Infantry matériel reserve. It was decided to concentrate most Allied production capacity for light tanks into the manufacture of a single type, and the Hotchkiss tank was chosen as it had the necessary mobility to be of use in the many armoured divisions the Entente planned to raise for the expected decisive summer offensive of 1941. To this end British and Portuguese heavy industry had to assist in producing the cast armour sections. It was hoped to increase production to 300 a month in October 1940, and even 500 a month from March 1941, the sections of 75 of which to be provided by Britain in exchange for a monthly delivery of nine Char B1s. This can be compared to the planned production of the R 40: 120 per month, reflecting the little importance now attached to infantry support.
These plans were disrupted by the Battle of France. In May 1940 the type equipped in the Cavalry units two tank regiments (of 47) in each of the three Mechanised Light Divisions and served as AMR in the 9th and 25th Mechanised Infantry Division (sixteen vehicles for each), 3rd DLM (22 "H35"s and 47 "H 39"s) and in three of the five Cavalry Light Divisions (sixteen vehicles each for the 1re, 2e and 3e DLC). Furthermore sixteen vehicles were part of the 1er RCA in Morocco. In the Infantry it equipped the two autonomous battalions mentioned above and two battalions of 45 in each of the three Divisions Cuirassées, the latter with the "H 39" variant. Most Hotchkiss tanks were thus concentrated in larger motorised units, in the armoured divisions supplementing the core of heavier tanks, though they were mismatched: the slower "H 35"s fought alongside the swifter SOMUA S35s, whereas the faster "H 39"s joined the slow Char B1s. The vast majority of these vehicles still had the short gun. Several ad hoc and reconstituted units were formed with the type after the invasion. These included 4e DCR (forty vehicles) and 7e DLM (47). Most of these later units were equipped with new vehicles built with the long gun, but 7e DLM also deployed twenty-two old "H 35"s in its 8e dragons-chars. In May deliveries peaked at 122; a recently discovered picture of a Hotchkiss tank with series number 41200 indicates that in June at least 121 were produced for a total of at least 1200 vehicles, not including prototypes.
About 550 Hotchkiss tanks were captured and used by the Germans as Panzerkampfwagen 35H 734(f) or Panzerkampfwagen 38H 735(f); most for occupation duty. Like the French, the Germans made no clear distinction between a "H 38" and a "H 39"; and fitted many with a cupola with a hatch.
The independent 211e Panzerabteilung was deployed in Finland during Operation Barbarossa. In 1944, three of its vehicles were converted to 7.5 cm self-propelled guns.
Additional vehicles were sent to Finland as part of the independent Panzerkampfwagenzüge (tank platoons) 217, 218 and 219, which were attached to the 20th Mountain Army in February 1942. The platoons were the same as those of Panzerabteilung 211, consisting of one SOMUA S35 and four Hotchkiss tanks. They were later disbanded, with the tanks being dispersed for use as fortifications and the crews used to form two batteries of Stug III Gs (741 and 742).
German H35/39s also saw action in Yugoslavia with 7.SS-Freiwilligen-Gebirgs-Division "Prinz Eugen", 12. Panzer-Kompanie z.b.V. and I./Panzer-Regiment 202. In addition, tanks used in France for various training and security units also got caught in the fighting in Normandy, such as Panzer Abteilung 206, Panzer –Ersatz und Ausb. Abt. 100, and 200. Beute-Sturmgeschütz-Abteilung.
In 1942 a project was launched make use French equipment as carrier platforms for heavier guns. The program was under the direction of Major Alfred Becker. Becker was an artillery officer who was a mechanical engineer by trade, and had previous experience making similar conversions with captured Belgian and British vehicles. Working at his Paris works 24 Hotchkiss tanks were in 1942 converted into a Marder I Panzerjäger (tank destroyer), the 7,5 cm PaK40(Sf) auf Geschützwagen 39H(f), and 48 into self-propelled artillery, the 10,5 cm leFH18(Sf) auf Geschützwagen 39H(f), all to be used by units in France. In addition, vehicles were modified into munition carriers or artillery tractors (Artillerieschlepper 38H(f)) or rocket-launchers (Panzerkampfwagen 35H(f) mit 28/32 cm Wurfrahmen). A special artillery observation vehicle was created: the Panzerbeobachtungswagen 38H (f). In June 1943, 361 Hotchkiss tanks were still listed in the German Army inventories as 37 mm gun tanks; this number had decreased to sixty in December 1944.
Three Hotchkiss tanks of the "H 39" version had been exported by France to Poland in July 1939 for testing by the Polish Bureau of Technical Studies of Armoured Weapons (Polish: Biuro Badan Technicznych Broni Pancernych). During the German invasion of Poland in 1939 the Hotchkiss tanks, together with three Renault R 35 tanks, were incorporated into an ad hoc "half company" unit of lieutenant J. Jakubowicz formed on 14 September 1939 in Kiwerce, Poland. The unit joined the task force "Dubno" and lost all of its tanks during the marches and fighting against German and Soviet armies.
Two vehicles were exported by France to Turkey in February 1940.
In 1943 the Germans, against objections, delivered nineteen "H 39"s to Bulgaria for training purposes, when it proved to be impossible to find 25 unmodified Panzer I light tanks, the type the Bulgarians really desired. After the war these vehicles were used by police units. In 1942 the Germans delivered fifteen vehicles to Hungary and a small number to Croatia.
In October 1942, the Hungarian Army received fifteen Hotchkiss "H 39" tanks, which formed the bulk of the 101st Independent Tank Company, which was used in the counter-partisan role. The unit operated in the Ukraine, Belarus and Poland and was finally disbanded after losing 30 % of its tanks to enemy action and having to blow up the rest due to lack of fuel and spares. The unit returned to Hungary from Warsaw in September-October 1944.
In North Africa 27 vehicles (thirteen H 35 and fourteen "H 39") were officially serving in the 1e Régiment de Chasseurs d'Afrique and were allowed to remain there by the armistice conditions; another five were hidden in Morocco. They fought the Allies during the opening stages of the Allied invasion of French North Africe near Casablanca in November 1942, destroying four M3 Stuart light tanks. The regiment then joined the allied cause and was re-equipped with M4 Sherman medium tanks in the summer of 1943.
After the war some Hotchkiss tanks were used by French security forces in the colonies and occupation forces in Germany. Ten "H 39s" were clandestinely sold to Israel – they were shipped from Marseilles to Haifa in 1948. At least one remained in service with the Israel Defense Forces until 1952.