Tumours in pets occur naturally and are common in dogs as they are in humans. Tumours of the alimentary system have been reported in animals, although less frequently. Food patterns and specific diet components could have a big role in such tumour occurrence. Therefore, the aim of this study was to investigate the clinical signs and inspect the neoplasm lesions of the gastrointestinal (GI) tract grossly and histopathologically in dogs in Baghdad, Iraq, and to see whether pet diets had any tumourigenic effect. Throughout two years sixteen dogs were referred to Teaching Animal Hospital and private clinics at Baghdad city with masses in (GI) tract. Males and large size breeds were more likely to be affected with GI tumours. Half of the cases aged 5-10 years and belonged to German Shepherd, while the other half involved the other breeds (i.e. Belgian Malinois, Labrador, Pointer GSP and Terrier) equally. Biopsies were taken from the tumour tissues for histological examination. Clinically, the animals presented general signs of digestive system abnormalities, like difficult defecating, bloody stool, lethargy and weight loss. Grossly, the tumours varied in their sizes from <3 cm to >5 cm in diameter, and the most frequent site of occurrence (10 out of 16 cases) was in the large intestine. Histologically, most tumours reported were malignant, and included adenocarcinomas (6/16) followed by leiomyosarcoma (4/16), adding to 2/16 belonged to carcinoid tumour. However, lipoma and viral papilloma (4/16) were also registered as benign tumours. In conclusion, tumours of canine digestive system do exist but rare. Healthy nutrition of dogs may prevent this type of cancer by consuming enough amount of raw meat, little artificial food, e.g. kibble along with some vegetables and fruits. Additionally, the information gained from dogs could be used to suspect and test the effect on humans as they have strong pathophysiology similarities.