Hangeshashinto is a traditional Japanese herbal medicine that is widely recognized for its efficacy in relieving mucositis induced by chemotherapy and radiotherapy. We herein present the cases of two patients with head and neck cancer who were clinically diagnosed with severe drug-induced interstitial lung disease (DILD) following Hangeshashinto administration for radiation-induced mucositis. Although Hangeshashinto has beneficial properties, it is also associated with a relatively low incidence of DILD, including some reports of death. To ensure patient safety, greater attention should be paid when prescribing Hangeshashinto, especially for elderly patients with factors predisposing them to develop severe DILD.