The invention relates to a transportation system for transporting at least one drive train component (7a, 7b, 7c) of a wind turbine (1) comprising a tower (2) and a nacelle (3) arranged on the top of said tower, said transportation system comprising a displacement system comprising one or more transportation rails (8, 8a, 8b) being arranged to support said at least one drive train component during displacement thereof, the displacement system facilitating displacement of the drive train component substantially parallel to the rotor axis between an installation location for the drive train component and a second location (10) by means of a first drive arrangement of said displacement system, and a second drive arrangement (11) mounted on said nacelle and comprising at least one winch (12), said second drive arrangement being separate to said displacement system and facilitating transportation of said drive train component between said second location and a lower level when connected to the drive train component independently of the operation of the displacement system. The invention furthermore relates to a wind turbine nacelle with a transportation system and a method of transporting a drive train component of a wind turbine.