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Background: This study evaluated carbon-ion radiotherapy (C-ion RT) for oral non-squamous cell carcmomas. Methods: We retrospectively obtained data from 74 patients who underwent C-ion RT for oral malignancies between April 1997 and March 2016. The C-ion RT was administered in 16 fractions at a total dose of 57.6 Gy or 64.0 Gy (relative biological effectiveness). Results: Forty-three patients had salivary gland carcinomas, 29 patients had mucosal melanoma, and 2 patients had other types of pathologies. The tumors were classified as Tl-T3 (24 cases), T4a (21 cases), or T4b (29 cases). The median follow-up was 49 months. The 5-year rates were 78.8% for local control, 36.2% for progression-free survival, and 58.3% for overall survival. Although 10 patients developed grade 3 osteoradionecrosis after C-ion RT, all patients maintained their mastication and deglutition functions after sequestrectomy and prosthesis placement. Conclusion: C-ion RT was effective for oral non-squamous cell carcinomas and had acceptable toxicities.