Background <p>Among several adverse events induced by chemotherapy for patients with far advanced and unresectable cancer, oral mucositis is one that reduces patient quality of life.</p> Objective <p>To evaluate the preventive effects of hangeshashinto on oral mucositis induced by chemotherapy.</p> Methods <p>We performed a comprehensive electronic literature search (PubMed, the Web of Science, and CENTRAL) up to March 2024 to identify studies showing the efficacy of hangeshashinto administration for preventing oral mucositis in patients receiving chemotherapy. To integrate the individual preventive effect of hangeshashinto, a meta-analysis was performed using random-effects models to calculate the risk ratio and 95% confidence interval, and heterogeneity was analyzed using <i>I</i>² statistics. In this analysis, oral mucositis was defined as more than grade 1 mucositis.</p> Results <p>This meta-analysis included six studies (five randomized controlled trials and one case-matched study) involving 293 patients with cancer receiving chemotherapy. Among 141 patients who received hangeshashinto during chemotherapy, 65 (46.1%) developed oral mucositis; in contrast, among 152 patients who did not receive hangeshashinto or received a placebo, 78 (51.3%) developed oral mucositis. The meta-analysis suggested that hangeshashinto may reduce the risk of oral mucositis (risk ratio = 0.86, 95% confidence interval = 0.73–1.00, <i>P</i> = 0.05, <i>I</i>² = 0%) compared with no hangeshashinto or placebo.</p> Conclusions <p>The results of this meta-analysis suggest that hangeshashinto may have a preventive effect against chemotherapy-induced oral mucositis. However, further well-designed randomized controlled trials are required to confirm its preventive efficacy.</p>