Malignant peripheral nerve sheath tumors (MPNSTs) are rare sarcomas of children and adolescents, and they are aggressive tumors with a high rate of local recurrence. We present a 15-year-old boy with neurofibromatosis type 1 (NF1), who had a giant MPNST on the right thigh taking into account the available literature. Diagnosis of MPNST may be delayed in NF1 patients due to confusion with a neurofibroma and/or a plexiform neurofibroma. Malignancy should be considered, especially in cases with big masses, with heterogeneous involvement, or in the presence of cysts or necrotic nodules. The aim of surgical treatment is complete surgical excision.