Superficially, the OF-40 appears very similar to versions of the German Leopard 1 with welded turrets (Leopard 1A3 & 1A4). The OF-40 does share some common components with the Leopard 1, which had also been produced under license by OTO Melara since 1974. The OF-40 follows a conventional modern tank design. The driver is located in the front-right of the hull, with ammunition storage and NBC overpressure system located to the driver's left. The turret is located toward the middle of the tank, with the gunner and commander on the right side of the turret, and the loader on the left.
The armament consists of a 105 mm main gun with a rifled, 52-calibre barrel, developed by OTO Melara exclusively for this vehicle. The cannon is equipped with a thermal sleeve, fume extractor and a semi-automatic breech mechanism and is aimed in both vertical and horizontal axes with an electro-hydraulic drive system. The main gun however is not stabilized. The cannon uses NATO-standard 105 mm ammunition with APDS (1470 m/s muzzle velocity), HEAT (1170 m/s), HESH (730 m/s), incendiary and smoke rounds. Two 7.62 mm machine guns make up the secondary armament: an electrically fired coaxial machine gun slaved to the main cannon and a second gun on an anti-aircraft pintle installed next to the loader's hatch on the turret.
The tank uses an advanced fire-control system developed by Officine Galileo. The commander's station was outfitted with an independently stabilized VS 580-B panoramic day/night sight with an 8x magnification, co-developed with SFIM of France. The sight is housed in an armoured turret located in front of the commander's hatch. The tank gunner uses an 8x C125 telescopic sight to lay fire from the main cannon and coaxial MG. This sight is co-aligned with a Selenia VAQ-33 laser rangefinder which has an effective range from 400 to 10,000 m.
The OF-40 is powered by a German-made MTU MB 838 Ca M500 diesel motor which provides an output of approx. 610 kW at 2,200 RPM. The MB 838 Ca M500 is a four-stroke, turbo-charged, 10-cylinder multi-fuel engine with a 90° Vee configuration and is coupled to a ZF transmission system with a fluid torque converter and an epicyclic gearbox with four forward and two reverse gears. The engine is liquid-cooled and further optimized for operation in arid environments with an automatic air-cooling system which detects overheating conditions and activates a cooling fan on the engine deck. The engine compartment also has an automatic fire-extinguishing system.
The running gear consists of 14 (2×7) rubber-rimmed double dished roadwheels, two idler wheels (at the front of the hull), two drive sprockets (rear hull) and ten (2×5) return rollers supporting two tracks. The tracks have a service life of approx. 2,500 km. The OF-40 rests on an independent torsion bar suspension system with hydraulic shock absorbers and friction dampers on the first, second, third, sixth and seventh pairs of roadwheels.
The tank can also drive under water to a limited depth using a snorkel to feed the engine and comes equipped with two water pumps rated at 120 l/min used to evacuate water from the tank during fording.