The present invention relates to a windshield washer fluid supply system (1) which enables the washer fluid tank (2) connected to the windshield (O) washing system in automobiles to be filled with rain water. The objective of the present invention is to provide a washer fluid supply system (1), which enables to clean the rain water by a filter (12) and store it for use as windshield washer fluid, enables addition of antifreeze to the washer fluid tank (2) depending on the collected rain water, and prevents entrance of the rain water into the washer fluid tank (2) when there is no antifreeze in the antifreeze tank (5).