Burning mouth syndrome (BMS) is a chronic oral pain disorder. There is a theory that BMS is a form of nociplastic pain. A standard treatment for BMS has not yet been established. Kampo medicine is a traditional oriental medicine. The purpose of this study is to evaluate the effectiveness of Rikkosan-a traditional Japanese herbal medicine (Kampo)-in the treatment of BMS. A single-center retrospective study was conducted on 20 patients who were diagnosed with BMS and treated with Rikkosan alone (total daily dose; 7.5 g) three times daily for approximately 4 weeks (29.5 ± 6.5 days). Rikkosan was dissolved in hot water and taken internally. They had an average age of 63 years, and 90% were being treated for other illnesses, but their medication status was the same during this study period, except for Rikkosan. No adverse events were observed in patients. Numerical rating scale (NRS) or visual analog scale (VAS)/10 scores decreased significantly between the time of the initiation of Rikkosan and one month after (-2.1 ± 1.2, < 0.05). Rikkosan has a short-term effect of reducing NRS by two levels in BMS patients.