The FT-17 was essentially a narrow armoured box with the driver at the front, turret with a traverse of 360° in the centre, and the engine and transmission at the rear. The driver entered the tank via twin doors over his compartment, whilst the commander/gunner entered via doors in the turret rear. Maximum armour thickness was 16mm (0.63in) and the hull was of riveted construction. The Renault FT-17 was the first tank with a turret that could be traversed through 360° to enter service. The suspension consisted of coil and leaf springs and pivoted bogies. There were nine small road wheels on four bogies, with the drive sprocket at the rear and the large idler at the front. The latter was of laminated wood with a steel rim. There were six return rollers. Most FT-17s were fitted with a tail at the rear of the hull to increase the trench-crossing capabilities of the tank, but this could be removed for transport.

From a very early stage it was decided that there would be four basic models of the FT-17. The first model to enter service was the Char Mitrailleur 8mm, which was armed with an 8mm machine-gun with an elevation of +35° and a depression of -20° 4,800 rounds of machine gun ammunition were carried. This was followed by the 37mm model, armed with a 37mm Puteaux gun with an elevation of +35° and a depression of -20°; 237 rounds of ammunition were carried - 200 HE, 25 AP and 12 shrapnel. The signals vehicle had no turret but was fitted with a superstructure, carrying a single radio, and had a crew of three (radio-operator, observer and driver). The self-propelled gun was called the Char Canon 75S and was armed with a 75mm gun in an open mount. This did not enter service, however. Subsequently many other variants were developed, including an amphibious version, bridgelayer, bulldozer, cargo carrier with redesigned hull, fascine carrier for crossing trenches (Char Fascine), mineclearing tank (Char Demineui), searchlight carrier (this had a searchlight on a high tower and was used for internal security operations by the French police after the war) and a smoke-laying tank. Most of these were for trials purposes, although some were used in the war.

The Renault FT-17 was first used in action on 31 May 1918, when 21 tanks supported infantry in the battle of the Forest of Retz. Later that day the Germans counter-attacked and most of the ground was lost again. At the end of the day only three FT-17s were still operational. Losses were heavy in many of the early engagements, but as the crews gained experience and tactics were improved, losses dropped considerably. By the end of the war just over 3,000 tanks had been completed and production continued for a short time afterwards. After the war the tank was used in action in most of the French colonies including Morocco, Syria and Tunisia.

One of the advantages of the Renault was that its small size enabled it to be transported by lorry from one part of the front to another, whereas the heavier tanks had to be brought up by rail and then proceed to the front line under their own power. After the end of the war many FT-17s were exported, and in many cases these were the first armoured vehicles of some armies. Such was the demand that eventually exports were stopped as the French Army would have ended up with no Renaults at all. In the 1920s many attempts were made to modernise the FT-17, and some were fitted with Citroen-Kegresse rubber band tracks, although these were for trials only. Further development by Renault resulted in the NC1 (or NC27) light tank which had an up-armoured hull and new suspension. This was tested by the French Army but was not adopted, though some examples were sold to Japan and Yugoslavia. This was followed by the NC2 (or NC31) which had a more powerful engine and weighed 9.5tons (9.653kg). Armament consisted of turret-mounted twin 7.5mm machine-guns, and some of this model were purchased by Greece. In the 1930s those FT-17s remaining in service were rearmed with new 0.75mm Hotchkiss machine-guns and then became known as the FT-31. These carried 3,600 rounds of standard ammunition plus a further 450 rounds of armour-piercing ammunition. There were still some 1,600 FT-17s in service when the Germans invaded France in 1940, and many of these were captured by the Germans. The Germans called them the PzKpfw 18R 730(f) and used them mainly for the internal security role and for guarding airfields and other strategic targets. Some of the tanks had their turrets removed, the turrets being installed in coastal defences. Some remain to this day in the Channel Islands.