Septic peritonitis, a common cause of abdominal distress associated with high mortality rates in dogs and cats, is often secondary to GI perforation and requires immediate medical and surgical treatment. This retrospective study reported risk factors and outcomes in 55 animals (44 dogs, 11 cats) treated surgically to identify prognostic factors for future treatment. The overall mortality rate was 63.6%, similar to previously published ranges. Patients with a history of antiinflammatory drug administration were likely to have a perforation at the level of the pylorus, although pyloric perforation did not significantly impact survival to discharge. Age, closed-suction drainage, recent previous abdominal surgery, and location of perforation did not impact short-term outcomes.