Abstract: An automatic water level control system, for use in conjunction with a Christmas tree stand of the type having a watering basin with an outer rim and a tree clamping mechanism for holding the Christmas tree in an upright manner with the base portion of the tree disposed within the watering basin. The water level control system includes a water supply container, a flexible conduit, an attachment mechanism, and a valve mechanism. The water supply container serves as a holding tank for water which is supplied to the watering basin of the Christmas tree stand via the flexible conduit. The water level in the watering basin is regulated by the valve mechanism attached to the Christmas tree stand. The attachment mechanism has a main body and is attachable to the outer rim of the watering basin in a manner to functionally secure the main body to the Christmas tree stand. The valve mechanism includes a watering port, a valve, and a float member.