A cross-bred dog was referred because of vomiting, diarrhea, weight loss and anorexia of one-month duration. Clinical findings, bloodwork (including fasting gastrinemia), abdominal ultrasound and US-guided cytological evaluation of the regional lymph nodes were suggestive of a neuroendocrine tumor, possibly a gastrinoma. Medical therapy (H(2)-inhibitors, omeprazole, gastroprotectants, somatostatin analogues) enabled to improve symptoms, thereby stabilizing the dog's conditions. Based on a CT scan, performed to define site and tumor extension, the pancreas was diffusely infiltrated and the regional lymph nodes were considered as metastatic. The dog underwent surgical debulking to reduce tumor burden and hormonal secretion. Histopathology and immunohistochemistry confirmed the diagnosis of gastrinoma. Multimodal treatment (including surgery and medical therapy) normalized gastrinemia and improved quality of life.