Background: Mucositis is an important adverse effect of cancer treatment. The aim of this study was to investigate the effect of ice cubes on oral mucositis following head and neck radiotherapy. Materials and Methods: A randomized controlled trial was conducted on 40 head and neck cancer patients who underwent radiotherapy. The patients were randomly divided into two experimental and control groups of 20 each. The patients in the experimental group received instructions for sucking ice cubes before and after each radiotherapy session for five minutes during the study period. Oral examinations were performed on the 1st, 7th, and 14th days of the study. Pain severity and mucositis were evaluated by a checklist and self-reported assessment by the patients at the above-mentioned intervals. Results: As time passed, the mean of pain intensity in the control group significantly increased (p<0.001), whereas the experimental group showed no significant difference during the study period (p>0.05). Patients’ self-assessment in the control group showed significantly higher oral discomfort during the study period (p=0.012). In contrast, self-assessment of patients in the experimental group exhibited no significant changes during the study (p>0.05). Conclusion: Although no significant difference was observed in mucositis intensity between the experimental and control groups, patients using ice cubes during radiotherapy sessions felt more comfort in their oral cavity.