BACKGROUND: Chemotherapy-induced oral mucositis (OM) is a common complication of cancer treatment that significantly impacts patients' quality of life. Butyrate, a short-chain fatty acid, has been shown to inhibit inflammation and mitigate intestinal mucosal damage. How, its effect in treating OM remains unclear. MATERIAL AND METHODS: OM model in mice pretreated with 5-FU solution was established by injecting 20% acetic acid into oral mucosa. Sodium butyrate was given for treatment. H&E staining was used to observe histopathological changes, and qRT-PCR to assess inflammatory factor level changes in ulcer tissues after treatment. Also, qRT-PCR and immunofluorescence staining were used to evaluate the expression and distribution of tight junction protein in ulcer tissues. RESULTS: Sodium butyrate treatment improved the weight loss in mice caused by OM and promoted the repair of oral mucosa in a time-dependent manner. In addition, sodium butyrate significantly inhibited the mRNA levels of inflammatory factors such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-18 (IL-18) in the ulcer tissue. Moreover, sodium butyrate promoted the mRNA and protein expressions of tight junction protein-1 (ZO-1) and Claudin-1 in the epithelial cells of the ulcer tissue. CONCLUSIONS: Butyrate promotes OM healing by reducing inflammation and increasing the expression of tight junction proteins in ulcer tissues.