Radiation therapy (RT) is increasingly utilized in conjunction with surgery for the treatment of retroperitoneal soft tissue sarcomas (RPS). Despite multiple theoretical advantages of RT, its role in the surgical management of this disease remains ill defined.Patients undergoing surgery for RPS from 1990 to 2011 were identified. Patients were classified as having primary or recurrent disease, and then further stratified by the use of perioperative RT. Primary outcomes, including overall survival (OS) and recurrence-free survival (RFS), were estimated using the Kaplan-Meier method with comparisons based on the log rank test. Cox-proportional hazards modeling was used to estimate the independent effect of RT on survival.Ninety-four patients met final inclusion criteria. After adjusting for confounding variables, perioperative RT remained independently associated with a reduced risk of recurrence (HR 0.34, P < 0.01) and death (HR 0.30, P = 0.02).In this retrospective series, perioperative RT is an independent predictor of improved OS and RFS. These results provide additional support for the use of RT in the multimodality treatment of retroperitoneal sarcoma.