Wilms' tumor is the most common kidney tumor of childhood. The outcome of this malignant tumor has improved due to the improvement of therapeutic strategies. The most important factor in determining the prognosis of these patients is the histopathology subtype of the tumor; unfavorable histopathology is seen in only 11.5% of the patients, which accounts for 52% of deaths. Therefore, the aim of this study was to determine the outcome of children with Wilms' tumor referred to our hospital over a period of 10 years. This is a retrospective cohort study, and the target population included all patients with Wilms' tumor referred to Ali Asghar Hospital and were treated according to the National Wilms tumor study 4 (NWTS-4) protocol. All patients' data were extracted from the medical records of the department. Overall survival and event-free survival (EFS) were analyzed by the Kaplan Mayer method in the SPSS software, version 23. Fifty-two patients (24 male and 28 female patients) with Wilms' tumor were included. The mean age of the subjects was 40 months. The most common stage among boys and girls was stage II (23.08% and 28.85%, respectively). Our findings revealed that the overall five-year survival of patients was 87±5%; this figure was determined as 100% for boys and 76.8% ± 1.6 for girls (P = 0.018). Our findings show a dramatic improvement in the outcome of children with Wilms's tumor, and our results are comparable with other results from developed countries. Gender may be an independent prognostic factor of children with Wilms' tumor.