Although rikkunshito was reported to be effective for treatment-resistant nonerosive gastroesophageal reflux disease (NERD), it is unclear which Rome IV subgroups of NERD patients benefit fromrikkunshito. This study investigated the efficacy of rikkunshito in patients with functional heartburn.Ten patients with functional heartburn who experienced symptoms of dyspepsia were enrolled and received rikkunshito for 8 weeks. The Frequency Scale for Symptoms of GERD (FSSG), the Japanese translation of the Quality of Life in Reflux and Dyspepsia (QOLRAD-J) questionnaire, and the Hospital Anxiety and Depression Scale (HADS) before, and 4 and 8 weeks after, administration were evaluated. Overall treatment efficacy (OTE) was evaluated at 8 weeks after administration.One patient voluntarily withdrew from treatment at 4 weeks. Total FSSG score was significantly (P = 0.039) lower 8 weeks after treatment or at discontinuation (13.2 ± 8.0) than before treatment (18.3 ± 10.7). Although QOLRAD-J score was higher 8 weeks after treatment or at discontinuation than before treatment, the difference was not significant different. HADS score was not significantly lower 8 weeks after treatment or at discontinuation, as compared with before treatment. However, total FSSG and HADS anxiety scores were positively correlated (correlation coefficient: 0.684, P = 0.027).The findings from this first study of the efficacy of rikkunshito for functional heartburn suggest that it might be effective in such patients.