A plumage color mutant, dotted white (DTW), of Japanese quail is described in this paper. The adult DTW mutant shows white plumage with a small colored spot on the head and/or back. The pigmented spots invariably appear on the dorsal region and never on the ventral region of the body. Some birds lack colored spots and show pure white plumage. The chick of the DTW mutant shows cream yellow plumules similar to those of the White Leghorn chick. Colored spots also exist as in adults, and its coloration is diluted light brown. The feathers on colored spots of the adult show diluted pigmentation as compared with wild-type feathers. In addition, the wheat-straw colored shaft streak is extremely narrow and the transversal bars are missing. The DTW mutant is thought to be genetically different from previously reported similar mutants, brown-splashed white, panda, and recessive white. Genetic analyses revealed that the DTW mutant plumage is controlled by an autosomal recessive gene. The gene symbol dtw is provisionally proposed, since there remains a possibility that the DTW character may be allelic to some of the similar mutant characters mentioned above.