BACKGROUND Sinonasal rhabdomyosarcoma (RMS) is a rare malignancy in children and adolescents. It is aggressive and locally invasive, and can require local postoperative radiotherapy. This report presents the case of a 16-year-old girl with a sinonasal-cutaneous fistula following excision and radiotherapy for rhabdomyosarcoma, which required reconstructive surgery using an expanded forehead flap. CASE REPORT We report the case of a16-year-old girl who was referred to our clinic with sinonasal-cutaneous fistula. Prior to presentation at our department, she presented with bilateral intermittent nasal congestion 3 years ago. At a local hospital, orbital computed tomography and nasal endoscopic biopsy revealed an embryonal rhabdomyosarcoma (ERMS). One month later, skull base tumor resection, nasal cavity and sinus tumor resection, and low-temperature plasma ablation were performed at a local hospital. Two weeks after the operation, the patient received intensity-modulated radiation therapy for a total of 50 Gy. Chemotherapy started 15 days after radiotherapy, using a vincristine, dactinomycin, and cyclophosphamide (VAC) regimen. Approximately 1 month later, an ulcer appeared at the nasal root and the lesion gradually expanded. The patient was referred to our hospital due to the defect. Firstly, a tissue expander was implanted at the forehead for 7 months. Then, the skin around the defect was trimmed and forehead flap was separated to repair the lining and external skin. The flap survived well 1-year after the operation. CONCLUSIONS This report highlights the challenges of post-radiation reconstructive surgery and describes how an expanded forehead flap can achieve an acceptable cosmetic outcome in a patient with a sinonasal-cutaneous fistula.