Objective: To identify physical exam findings, clinicopathological parameters, time to surgery, empirical antimicrobial use, and culture results that could be associated with outcome in cats with septic peritonitis (SP). Design:Retrospective cohort study of cats from 2002 to 2015.Setting: Four university teaching hospitals.Animals: Eighty-three cats diagnosed with SP by cytology or culture. Interventions: NoneMeasurements and Main Results: Fifty-eight cats survived to discharge (69.9%); 1 cat was euthanized in surgery; 20 were euthanized postoperatively; 4 cats suffered cardiac arrest after surgery.The most common etiology of SP was secondary SP due to gastrointestinal perforation (49.4%), followed by primary SP (22.3%). Mean blood glucose concentration was significantly different between survivors and nonsurvivors (P = 0.006). Cats that received appropriate empirical antibiotic therapy were 4.4 times more likely to survive than cats that did not receive appropriate antibiotics (P = 0.018). Conclusions:As previously documented, SP secondary to gastrointestinal leakage was the most common etiology. In this population, cats with a higher blood glucose concentration on presentation had a worse prognosis. Cats that received appropriate empirical antimicrobial therapy were more likely to survive. K E Y W O R D Sgastrointestinal, hyperglycemia, primary peritonitis, sepsis