This case report documents clinical and molecular findings in two littermate kittens of the Japanese domestic cat with GM2 gangliosidosis variant 0. Analysis included detailed physical, magnetic resonance imaging, biochemical, pathological and genetic examinations. At first, these littermate kittens showed typical cerebellar signs at approximately 2 months of age. About 2 months later, they progressively showed other neurological signs and subsequently died at about 7 months of age. Magnetic resonance imaging just before the death showed an enlarged ventricular system, T1 hyperintensity in the internal capsule, and T2 hyperintensity in the white matter of the whole brain. Histological findings suggested a type of lysosomal storage disease. Biochemical studies demonstrated that the kittens were affected with GM2 gangliosidosis variant 0, and a DNA assay finally demonstrated that these animals were homozygous for the mutation, which the authors had identified in a different family of the Japanese domestic cat. The findings in the present cases provide useful information about GM2 gangliosidosis variant 0 in Japanese domestic cats.