A turret mooring system for a vessel which includes a concrete hull and a moonpool which extends generally vertically through the hull comprises a turret which is positioned in the moonpool, an upper bearing substructure which is mounted to the hull proximate an upper end of the moonpool, and an upper bearing which includes a non-rotatable part that is connected to an upper end portion of the turret and a rotatable part that is connected to the upper bearing substructure. Thus, the turret is rotatably connected to the hull via the upper bearing and the upper bearing substructure.