Introduction: Malignant peripheral nerve sheath tumors (MPNST) are rare tumors that originate from Schwann cells. Patients with neurofibromatosis type 1(NF1) are prone to develop these tumors. Due to their rarity and lack of established treatment, the prognosis of MPNST is poor. Here, we reviewed the clinical data and outcome of patients diagnosed with MPNST in our institution. Materials and Methods: A retrospective medical record study was conducted on children treated for pathologically confirmed MPNST at the Seoul National University Children’s Hospital, between January 2007 and December 2016. Results: Eleven patients (7 boys and 4 girls) were diagnosed with MPNST at a median age of 12 years and 10 months. From the entire study population, eight patients (73%) presented NF1. The median size of the tumor was 8.5 cm (range, 0.6 cm to 18 cm). Four patients (36%) presented metastases at the diagnosis. All the patients underwent chemotherapy with various therapeutic combinations and received surgical resection. Two patients (18%) received local radiotherapy. Five patients (45%) relapsed and 2 of them (40%) did not survive. The median follow-up period was 18.8 months (range, 2.3 months to 167.1 months). The 2-year overall survival rate was 72.7% (95% confidence interval 45.2-100%), and the 2-year event-free survival rate was 58.2% (95% confidence interval 33.0-100%). In this study, univariate analysis was performed to assess the correlations between the clinical factors that affect the survival and recurrence events. There was no statistically significant difference in the overall survival rate according to the patients’ clinical factors. However, there was a decreasing trend in the relationship between the event-free survival rate and the prevalence of NF1 (75% versus 0%, p value=0.06). Conclusion: MPNST are rare and highly aggressive tumors, for which there is no established treatment. Our study documents a decreasing trend in the event-free survival rate in patients with NF1. The early relapse detection of MPNST is insured by the regular follow up of NF1 patients, and further genetic studies of MPNST would be needed to find a better treatment strategy.