A wind turbine having a cooling system, which wind turbine includes a nacelle in connection with which one or more wind turbine components are arranged, is disclosed. The cooling system includes at least one cooling circuit arranged to lead a heat transfer medium to and from one or more of the wind turbine components, at least one cooling device arranged to cool the heat transfer medium, at least one pump arranged in connection with the at least one cooling circuit to circulate the heat transfer medium in the cooling circuit, and at least one medium tank arranged in connection with the cooling circuit. The at least one medium tank is arranged inside the nacelle.