A urea filler neck for preventing a urea overflow includes a filler housing forming a urea path in which urea flows to a urea tank. An injection gun guide is provided in the filler housing. An end of an injection gun is fixed by the injection gun guide to limit an insertion position of the injection gun inserted into an inlet of the filler housing. An injection gun guide flooding phenomenon is generated, in which urea flowing backward from the urea tank rises to block an air flow in the filler housing being generated in the injection gun guide. A filler housing pressure increasing phenomenon is generated, in which a pressure in the filler housing is increased due to blocking of the air flow by the injection gun guide flooding phenomenon being generated in the injection gun guide.