A device for changing a compression ratio of an internal combustion engine is provided. The engine has a crank drive with a crankshaft with at least one crank pin, mounted in a rotationally movable fashion, connected to a connecting rod and a piston arranged in a cylinder of the internal combustion engine. In order to convert rotational movement of the crankshaft into a bidirectional movement of the piston with a defined stroke height, a rotationally movable, externally toothed eccentric for changing the piston stroke height is arranged between the crank pin and an eyelet on the connecting rod. In order to rotate the eccentric, an externally toothed first gearwheel is axially connected in a rotationally fixed fashion to a second gearwheel via a shaft arranged parallel to the crankshaft which is arranged in a meshing fashion on a third gearwheel which can be rotated by an actuating element.