A motor-adjustable steering column for a vehicle includes a supporting unit attachable to a vehicle body and by which there is held an adjusting unit in which a steering spindle is mounted so as to be rotatable about a longitudinal axis. An adjustment drive is connected to the supporting unit and to the adjusting unit and is adjustable relative to the supporting unit. The adjustment drive includes a drive unit and a threaded spindle which engages in a spindle nut and which has a threaded spindle axis. The threaded spindle and the spindle nut can be driven to rotate relative to one another about the threaded spindle axis by the drive unit. To prevent slipping or spinning of the spindle drive in a crash situation the adjustment drive includes a blocking device which can be brought into a blocking position for blocking the threaded spindle relative to the spindle nut.