An 1-year-old male Basset Hound dog was evaluated for chronic intermittent vomiting, hematemesis, and melena which had been ongoing for several months. The histopathologic examination revealed that all layers of the small intestine were thicker than normal. The lamina propria of the mucosa, including the villi, exhibited a prominent cellular infiltrate which consisted of numerous eosinophils and an increased numbers of plasma cells in addition to the normal lymphocytic component. The muscularis mucosa was invaded, and in some places disrupted, by eosinophils, which also infiltrated into the submucosa and muscularis propria. This report describes the pathological findings of a case of eosinophilic gastroenteritis (EG) in a dog.