Test flights commenced on 28 December 1915, but were interrupted by bad weather in St Petersburg, where the Lebed factory was located.

Before production began, a number of handling difficulties noted by the test pilots were being corrected in the design, along with a new set of problems caused by a change in powerplant.

These heavier powerplants shifted the aircraft's centre of gravity, and the mountings for the engine and cooling system had to be revised before a final round of tests began in October.

In particular, a number of engine fires and crashes due to structural defects led to deliveries of the type being suspended by mid-year while an investigation was held.

The Lebed XII saw limited frontline service in the North and North-western parts of the front with Germany, equipping four air divisions of the 38th Corps, 5th Army.