Background: The current pooled analysis evaluated the efficacy of Hangeshashinto (TJ-14) in the prevention and/or treatment of chemotherapy-induced oral mucositis (COM) in gastric cancer and colorectal cancer using two prospective, multi-institutional, randomized, double-blind, placebo-controlled phase II trials. Patients and Methods: HANGESHA-G and HANGESHA-C randomly assigned patients with gastric cancer or colorectal cancer who developed moderate to severe COM (grade ≥1) during any cycle of chemotherapy to receive either TJ-14 or a placebo as a double-blind trial. The patients received a placebo or TJ-14 for four to six weeks, according to the chemotherapy regimen, from the start of their next course of chemotherapy. The primary endpoint was the incidence of grade ≥2 COM in the protocol treatment course, and the secondary endpoints were the time to disappearance of COM and the incidence of adverse events. Results: The pooled population included 181 patients. The incidence of grade ≥2 COM in the TJ-14 group was 55.7% (49 patients), while that in the placebo group was 53.8% (50 patients); there was no significant difference between the two groups (p=0.796). The median time to remission of grade ≥2 COM to grade <1 was 8 days in the TJ-14 group and 15 days in the placebo group (p= 0.072). The hazard ratio was 1.54 [1.02 to 2.31] in favor of TJ-14. Treatment with TJ-14 was associated with marginally significant reduction in the duration of severe grade ≥2 COM in comparison to patients receiving placebo indicating the effect of TJ-14 in reducing the severity of COM. Conclusion: The present-pooled analysis showed that TJ-14 had a treatment effect in gastric cancer and colorectal cancer patients with COM in comparison to a placebo. Further phase III studies with a larger sample size are needed to clarify the protective effects of TJ-14 against COM.