Stomach neoplasms represent less than 1% of canine cancer, and most common malignant epithelial tumors. The adenocarcinoma is 60 to 70% of gastric cancer. Affect older animals, with an average age of 8 years. There seems to be no racial bias, while higher incidence occurs in Collie, Staffordshire Terrier and Belgian Shepherd. The duration of clinical signs is for weeks or months, including vomiting, anorexia, weight loss, hematemesis, melena, abdominal pain and anemia. At ultrasonography, the gastric cancer show focal or diffuse thickening of the wall variable, often irregular, with loss of architecture of the wall. Regional lymphadenopathy can be identified. The definitive diagnosis requires histopathology. At necropsy the lesions are cerous appearance, with a firm of serosa and whitish due to the marked content conjuctiva. May be diffusely infiltrative, expandable, with central ulceration or polypoid. The adenocarcinoma spread to regional lymph nodes. Except in lymphomas, surgery is the most common form of treatment. The prognosis is unfavorable for the advanced nature during the diagnosis. We report a case of gastric cancer in dogs, suggested by history and by ultrasonography and confirmed by histopathology. A Pet's Cão Veterinary Clinic--Campo Grande-MS, requested the service of mobile ultrasound SUL-VET, evaluation of a male Labrador dog, 9 years, with a history of vomiting there 6 months, progressive weight loss, which was found diffuse thickening of the gastric wall (2.4cm) with loss of architecture of the layers, accentuation of the gastric folds, reduction in lumen and lymphadenopathy peripheral (1.2cm). The autopsy revealed marked thickening of the wall and diffuse gastric, mesenteric lymphadenopathy. Nodulations were not detected in other organs. Macroscopically the gastric wall showed up hard, with loss of elasticity and usually whitish to cutting surface. Microscopic examination revealed intense proliferation of gastric glands infiltrating into underlying layers, reaching serous body. In stained with periodic acid-Schiff presence of PAS positive mucous cells was pronounced. In gastric lymph nodes was observed sharp number of tumor cells, similar to those described in the stomach. Despite the gastric tumors are rare, should be considered in the differential diagnosis of elderly dogs with a history of chronic vomiting. While the ultrasound does not differentiate the type of epithelial tumor, is a useful tool for detection and diagnosis of gastric cancer.