[1] Designed for use as a night bomber, it was adapted to other roles, including that of a civilian airliner, following a lack of interest from the French Air Force.

The LeO 12 was a large biplane of a conventional design, with three-bay equal-span wings and twin engines mounted in nacelles on struts in the interplane gap.

[1] The Lioré et Olivier LeO 12 was a large biplane that was broadly conventional in terms of its design, which was relatively simplistic and, aside from its covering, was made entirely of metal.

[2] While principally intended for use by military operators in the night bomber role, for which it was to have been crewed by either two or three personnel, it was also readily convertible into a commercial airliner configuration, capable of carrying a maximum of 15 passengers along with up to 300 kg (661 lb.)

Directly behind the cockpit was a turret armed with twin machine guns while a second gunner's position was present within the fuselage, thus permitting both forward and aft defensive fire as required.

[4] It was typically powered by a pair of Lorraine-Dietrich 12Db engines, each capable of generating up to 400 HP, which enabled the aircraft to attain its maximum speed of 204 kmph (127 mph) while baring a payload of 1,944 kg (4,286 lb.)

A series of double-steel turnbuckles, each one attached to the base of the rearmost upright of the fuselage as well as to the spar of the plane, were used to secure parts of the tail unit; the lower end was integral with the rudder post and braced by two compact oblique struts.

The incidence of the stabilizer could be adjusted mid-flight, an ability which, when appropriately set by the pilot, meant that no force would need to be exerted on the control stick.

[11] After the French Air Force failed to quickly solidify their interest in the type as a bomber, three of the four aircraft built were modified for other roles.