An 11-year-old, castrated male Miniature Poodle dog was referred due to daily plant eating followed by vomiting for 7 years. Each time the dog went out for a walk, he had been munched grass, and then vomited. There were no abnormal findings on medical examinations. Through behavior examination and consultation, we diagnosed this dog as having a plant eating problem. Because we assumed that the dog had eaten plants to supply of dietary deficiency or relieve digestive problems, advised the owner to discontinue supplying previous diet and to feed high-fiber diet. On the follow up, the owner said that the dog had not eaten plants and vomited from 3 days after initial dietary change. The dog has not shown any clinical signs for 13 months. This clinical finding shows a possibility that deficient diet, especially fiber, relates to the plant eating behavior of a dog.