BACKGROUND: Omentoplasty is a commonly performed procedure after abdominoperineal resection for rectal cancer, but its effectiveness to reduce pelviperineal complications is not firmly established. OBJECTIVE: This study aimed to assess the impact of omentoplasty on postoperative outcomes after long-course (chemo) radiotherapy and abdominoperineal resection in patients with locally advanced and locally recurrent rectal cancer. DESIGN: Retrospective cohort study. SETTINGS: Single center. PATIENTS: All patients with locally advanced and locally recurrent rectal cancer undergoing abdominoperineal resection after neoadjuvant (chemo)radiation in a tertiary referral center between 2008 and 2020 were retrospectively reviewed. MAIN OUTCOME MEASURES: Multivariable logistic and linear regression analyses were performed to analyze the association between omentoplasty and pelviperineal complications, duration of nasogastric tube drainage, and length of hospital stay. RESULTS: A total of 305 patients were analyzed, of whom 245 underwent omentoplasty (80%). Pelviperineal complications occurred in 151 patients (50%) overall, in 125 patients (51%) with omentoplasty, and in 26 patients (43%) without omentoplasty. Independent predictors of pelviperineal complications in multivariable analyses were smoking (OR 2.68; 95% CI, 1.46–4.94) and high BMI (OR 1.68; 95% CI, 1.00–2.83), but not omentoplasty (OR 1.36; 95% CI, 0.77–2.40). The mean duration of nasogastric tube drainage was longer after omentoplasty (6 vs 4 d) with a significant association in multivariable analysis (β coefficient 1.97; 95% CI, 0.35–3.59). Patients undergoing omentoplasty had a significantly longer hospital stay (14 vs 10 d), and omentoplasty remained associated with a prolonged hospital stay after adjusting for confounding (β coefficient 3.05; 95% CI, 0.05–5.74). LIMITATIONS: Retrospective design. CONCLUSION: Omentoplasty was not associated with a reduced risk of the occurrence of short-term pelviperineal complications after abdominoperineal resection in patients undergoing long-course (chemo)radiotherapy. Furthermore, in patients undergoing omentoplasty, prolonged duration of nasogastric tube drainage and hospital stay was observed. See Video Abstract at http://links.lww.com/DCR/C124. OMENTOPLASTIA EN PACIENTES SOMETIDOS A RESECCIÓN ABDOMINOPERINEAL DESPUÉS DE QUIMIORRADIOTERAPIA DE CURSO LARGO PARA EL CÁNCER DE RECTO LOCALMENTE AVANZADO Y LOCALMENTE RECURRENTE: ESTUDIO DE COHORTE COMPARATIVO DE UNA SOLA INSTITUCIÓN ANTECEDENTES: La omentoplastía es un procedimiento que se realiza comúnmente después de la resección abdominoperineal por cáncer de recto, pero su efectividad para reducir las complicaciones pelvicoperineales no está firmemente establecida. OBJETIVO: Evaluar el impacto de la omentoplastía en las complicaciones pelvicoperineales a corto plazo y los resultados postoperatorios después quimioradioterapia de curso largo y resección abdominoperineal en pacientes con cáncer de recto localmente avanzado y localmente recurrente. DISEÑO: Es...