Malignant triton tumor is a divergent malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation. We report a case of malignant triton tumor arising in the brachial plexus of a 28-year-old women with neurofibromatosis type 1. Fluorodeoxyglucose-positron emission tomography-computed tomography before excision demonstrated a tumor with a maximum standard uptake value of 21 at 4 hours postinjection. The patient underwent complete excision of the tumor through median sternotomy and left supraclavicular approach. Adjuvant radiotherapy and chemotherapy were planned but the patient died of metastatic disease within 3 months of surgical resection.