Background and aims: Sigmoid diverticular disease has great clinical importance due to its increasing incidence in the Western world and a broad spectrum of clinical features with potential fatal complications after surgery. The definition of risk factors associated with postoperative infections, surgical complications and mortality could be helpful in clinical decision-making and optimizing perioperative treatment. Materials and methods: Based on a prospective database, 168 consecutive patients undergoing surgery for sigmoid diverticulitis were included in this study. The association of different potential risk factors such as age, Hinchey classification, type and duration of operation, surgeons' experience, blood loss, comorbidities, and hospital course with perioperative complications and mortality were tested by univariate and multivariate analysis. Results: Of the 168 patients enrolled in this study, there were 84 male and 84 female. A third of patients were operated as emergency cases (within 24 h after surgical evaluation); 62% underwent open surgery, 35% were treated laparoscopically with a conversion rate of 3%. A blood transfusion received 14% of patients, a surgical infection occurred in 20%, surgical complications appeared in 24% with a necessity for re-exploration in 9.5%. Leakage of the primary anastomosis was seen in 3.3%, whereas a leakage of the Hartmann's stump occurred in 4.3%. Overall in-hospital mortality was 4.1%. Multivariate analysis demonstrated Hinchey classification and intraoperative blood transfusion to be independently associated with postoperative infections, complications and mortality. Conclusion: Hinchey classification and intraoperative blood transfusion are independently associated with a worse perioperative outcome in patients undergoing surgery for sigmoid diverticular disease. While Hinchey classification cannot be influenced per se by the surgeon, outcome might be influenced by reducing the need for intraoperative blood transfusion.