An 11 yr old spayed female Maine coon cat was referred with uncontrolled diabetes mellitus. The cat had a 2 mo history of weight loss and intermittent vomiting. An abdominal ultrasound identified the presence of a large cavity measuring a maximum of 4.6 cm in the pancreas that was filled with a homogeneous echogenic fluid. Cytological analysis and culture of the fluid obtained from the pancreatic mass indicated the presence of a bacterial abscess. The application of nonsurgical drainage and the administration of glargine insulin and antibiotics resolved the clinical signs. The size of the pancreatic abscess was reduced after 5 mo, and the cat achieved diabetic remission and remained healthy at the time this report was prepared. This case report describes the successful treatment of a pancreatic bacterial abscess concurrent with diabetes mellitus in a Maine coon cat.