Objectives: The objective of this network meta-analysis is to optimize the prophylactic treatment for radiotherapy-induced oral mucositis in patients with head and neck cancer (HNSCC) receiving postoperative or definitive radiotherapy with or without chemotherapy. Materials and methods: We searched electronic databases to identify all eligible randomized clinical trials on oral mucositis. The endpoint was grade 0-2 oral mucositis. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were extracted. Network meta-analysis was performed using the frequentist approach to conduct multiple treatment comparisons. Results: In total, 57 trials with 5261 patients were eligible for this study. Both direct and network meta-analysis revealed that low-level laser additional to standard oral care (SOC) was better than most of the other treatments and achieved the highest effect on grade 0-2 oral mucositis, with a surface under the cumulative ranking curve (SUCRA) of 95.8%; however, SOC with or without placebo had worse effect than most of the other treatments and was ranked worst (SUCRA = 0.4%). Moreover, sensitivity analysis performed after we had combined the SOC and placebo groups (non-medication treatment, NMT) yielded similar results, with SUCRA of 91.3% and 3.5% for low-level laser and NMT, respectively. Conclusions: Low-level laser additional to SOC may be a more effective prophylactic treatment for reducing severe radiotherapy-induced oral mucositis; SOC alone is insufficient for patients with HNSCC receiving postoperative or definitive radiotherapy with or without chemotherapy.