To clarify the efficacy and feasibility of proton beam therapy (PBT) for olfactory neuroblastoma (ONB).We retrospectively reviewed 42 consecutive patients who received PBT with curative intent for ONB at National Cancer Center Hospital East from November 1999 to March 2012.Five patients (12%) had Kadish A disease, nine (21%) had Kadish B, and twenty-eight (67%) had Kadish C. All patients except one received a total dose of 65Gy (relative biological effectiveness: RBE) in 26 fractions. Twenty-four patients (57%) received induction and/or concurrent chemotherapy. The median follow-up for all eligible patients was 69months (7-186). The 5-year overall survival (OS) and progression-free survival (PFS) rates were 100% and 80% for Kadish A, 86 and 65% for Kadish B, and 76% and 39% for Kadish C, respectively. The sites of the first progression were local in six patients (30%), regional in eight (40%), distant in two (10%), local and regional in two (10%), and local and distant in two (10%). Late adverse events of grade 3-4 were seen in six patients (ipsilateral visual impairment, 3; bilateral visual impairment, 1; liquorrhea, 1; cataract, 1).PBT was a safe and effective modality for ONB.