Postoperative peritonitis (POP) is a serious complication of abdominal surgery, associated with high morbidity and mortality despite advances in diagnosis and treatment. The objective of this study was to describe the diagnostic, therapeutic, and outcome aspects of POP in the visceral surgery department of Avicenne Military Hospital in Marrakech. A retrospective study was conducted on 30 cases collected between January 2020 and December 2024. All patients included had undergone reoperation for confirmed peritonitis following abdominal surgery. The mean age was 47.9 years, with a balanced sex ratio. Major comorbidities included diabetes, obesity, and neoplastic diseases. The predominant causes were anastomotic leakage (43.3%) and visceral perforation (30%). Diagnosis was based on abdominal pain, fever, leukocytosis, and computed tomography (CT). Treatment involved early surgical reintervention, peritoneal lavage, and appropriate antibiotic therapy. Observed mortality remained significant, influenced by the timing of diagnosis, multiorgan failure, and patient condition. POP remains a major medico-surgical emergency requiring a multidisciplinary approach, early detection, and optimized treatment to improve survival.