Background: We conducted a retrospective analysis to investigate the clinical outcome of combined modality therapy using multiagent chemotherapy, nephrectomy, and radiotherapy in treatment of children with Wilms' tumor.Methods: This study was conducted on 91 cases of newly diagnosed Wilms' tumor from January 2001 until February 2012. Patients were categorized into two groups according to treatment approach: i) preoperative chemotherapy with delayed surgery (group A; n=66) and ii) immediate surgery (group B; n=25).Results: Preoperative chemotherapy showed a 54.5% partial response rate in group A patients. A final stage distribution indicated that the majority of patients (64%) from both groups were considered to be in the early disease stages (I and II). The median follow up was 49 months (range 3-124). The five-year overall survival rate was 66.5%, whereas the event-free survival rate was 62.5%. In univariate analysis, factors associated with statistically significant reduction in overall (P24 months was associated with a significant reduction in the overall survival rate (P=0.038, HR: 0.438, 95% CI: 0.192-0.953), but was not significant in terms of event- free survival (P=0.104, HR: 0.539, 95% CI: 0.256-1.136). Age >24 months (P=0.0095), disease stage (P=0.0014), and blastimal subtype (P=0.006) were associated with significant increases in relapse rate.Conclusion: Preoperative chemotherapy resulted in a final stage redistribution that placed the majority of patients in the early stages of the disease. Age at diagnosis, disease stage, and histological subtype significantly affected survival and relapse rates.