A case of gastric adenocarcinoma signet ring cell type was described in a ten-year-old female Jindo dog having about three months history of vomiting, anorexia and weight loss. On radiology, ultrasonography and computed tomography, thickness of the gastric fundus was irregularly increased. On necropsy, the gastric fundus was markedly thickened and gastric rugae were attenuated. The cardia and distal esophagus were also thickened. On histopathology, the mucosa was obliterated by neoplastic proliferation of round to polyhedral cells. The neoplastic cells had abundant vacuolated cytoplasm containing mucin. The neoplasm was infiltrated into the submucosa and muscle layer. Metastatic focus was not observed.