The design of the Type 89 was relatively conventional with a forward-mounted gun turret carrying the main armament, a Type 90 57 mm gun that was complemented by two Type 91 6.5 mm machine guns. One was located in the front hull and the other placed in a turret ball mount pointed towards the rear, a practice followed with most Japanese tanks. The Type 90 57 mm tank gun had a barrel length of (L14.9) el angle of fire of −15 to +20 degrees, AZ angle of fire of 20 degrees, muzzle velocity of , and could penetrate of 20 mm of armor at 500 m (0.8 in/550 yd). During the later stages of World War II, HEAT shells were developed to provide greater penetration of enemy armor.