BACKGROUND: For patients with advanced head and neck cancer (HNC) chemoradiotherapy (CHRT) is the main treatment option. CHRT is a severe treatment with a high ratio of side effects which may be even more pronounced due to mucosities related malnutrition. Nutritional intervention like nutritional counseling (NC) and oral nutritional supplements (ONS) may prevent malnutrition. A systematic review and meta-analysis was performed to assess the effect of NC with or without ONS (NC±ONS) on CHRT-related grade ≥3 mucositis in patients with HNC undergoing CHRT. METHODS: PubMed/MEDLINE, Web of Science, and Scopus were searched to identify randomized and non-randomized clinical studies of HNC patients undergoing CHRT, where mucositis grade ≥3 data were provided. Comparative and proportional meta-analyses were performed to calculate the odds ratio (OR) and incidence of a mucositis grade ≥3 in the included studies (%) with 95% confidence intervals (95% CI). RESULTS: There were seven studies fulfilling inclusion criteria with 655 participants included. NC±ONS revealed no risk reduction of grade ≥3 mucositis (OR: 1.2, 95%CI: 0.7-1.9). The overall mucositis rate was 38.3% (95% CI: 24.8%-52.6%) and 32.8% (95% CI: 14.9%-53.5%) (P = 0.67) in NC+ONS and NC-ONS respectively. CONCLUSION: Despite the undeniable role of NC±ONS for patients with HNC undergoing CHRT, we found it insufficient to avoid grade ≥3 CHRT-related mucositis. Further research should be conducted to determine recomendations how to decrease the risk of oral mucosities and, in consequence, how to prevent malnutrition in patients with CHRT.