Oral mucositis is a debilitating side effect of cancer treatment for which there is not much successful treatments at yet. We evaluated the effectiveness of topical morphine compared with a routine mouthwash in managing cancer treatment-induced mucositis. Thirty head and neck cancer patients with severe mucositis (World Health Organization Grade III or IV) were randomized into the morphine and magic mouthwash groups. Patients received morphine sulfate 2% or magic solution (contained magnesium aluminum hydroxide, viscous lidocaine, and diphenhydramine), 10 ml for every 3 h, six times a day, for 6 days. Both groups received same dietary and oral hygiene instructions and care. Mucositis was graded at baseline and every 3 days after treatment. Patients' satisfaction and drug effect maintenance were also evaluated. Twenty-eight patients (mean age of 49.5 ± 13.2 years, 63.3% female) completed the trial; 15 in the morphine group and 13 in the magic group. There was a decrease in mucositis severity in both of the morphine (P < 0.001) and magic (P = 0.049) groups. However, at the 6(th) day, more reduction was observed in mucositis severity in the morphine compared with magic group (P = 0.045). Drug effect maintenance was similar between the two groups, but patients in the morphine group were more satisfied by their treatments than those in the magic group (P = 0.008). Topical morphine is more effective and more satisfactory to patients than the magic mouthwash in reducing severity of cancer treatment-induced oral mucositis. More studies with larger sample size and longer follow-up are required in this regard.