An adjusting drive for a motor-adjustable steering column for a motor vehicle, includes a motorized drive unit and an external threaded spindle which has an external thread and a coaxial internal thread into which an internal threaded spindle engages. The external threaded spindle and the internal threaded spindle can be driven in rotation relative to one another about an axis by the drive unit. In order to provide an adjusting drive which requires a reduced drive torque and delivers an optimized free adjustment path, the external threaded spindle engages with its external thread in a drive nut, wherein the drive nut or the internal threaded spindle is able to be driven in rotation by the drive unit and is supported relative to the drive unit in the direction of the axis.