This case report describes the presentation, clinical signs, diagnostic evaluation and treatment of a three-year-old intact male German Shepherd Dog (GSD) that presented to the Cornell University Hospital for animals with a one-month history of diarrhea, light-color stools, lethargy and weight loss. Based on the dog's signalment, clinical signs and low trypsin-like immunoreactivity (cTLI) test, the dog was diagnosed with exocrine pancreatic insufficiency (EPI). Based upon serum levels of cobalamin and folate, the dog also had evidence of a small intestine bacterial overgrowth (SIBO), a common sequela of EPI in dogs. The dog was treated with oral pancreatic enzyme replacement, antibiotics, and cobalamin supplementation. The dog is currently responding well to treatment with a cessation noted in his major clinical signs (weight loss, diarrhea and lethargy).