This case report describes a 9-year-old female spayed miniature poodle mix diagnosed with a ruptured gallbladder mucocele. The dog had been diagnosed with a ruptured gallbladder by its primary care veterinarian and was referred to Cornell for further evaluation and treatment. Bloodwork showed a leukocytosis with neutrophilia, hyperbilirubinemia, and elevations in liver enzyme activity. Exploratory laparotomy revealed a biliary mucocele and focal biliary peritonitis. A cholecystectomy was performed and the dog recovered well from surgery. Postoperatively, the patient regurgitated, developed disseminated intravascular coagulation, neurologic signs, and died two days later. Necropsy revealed fibrinizing necrosis of the common bile duct and peritonitis. The cause of death was determined to be bile peritonitis leading to systemic inflammatory response syndrome and multi-organ failure. The current diagnostic and treatment methods for gallbladder mucocele will be highlighted in the following report.