BACKGROUND: In our study, it was aimed to histopathologically investigate the effects of chitosan on wound healing in the oral mucosa by applying the gel form of experimentally induced diabetes mellitus. METHODS: In our study, 42 male Sprague Dawley rats weighing 340±20 g, 14-16 weeks old, were used. Diabetes induction was achieved by administering 55 mg/kg streptozotocin intraperitoneally (i.p.) to 32 of the subjects. Those with blood glucose levels above 250 mg/dl as measured at the end of the 2nd and 7th days were considered diabetic and included in the study. Afterwards, a wound of 5 mm in diameter and 1 mm in depth was created in the buccal mucosa of the experimental animals with a disposable punch biopsy tool. Wound healing was evaluated on the 2nd and 5th days after the surgical operation. The samples were evaluated histopathologically in terms of inflammation, fibrosis, epithelial regeneration, necrosis, and foreign body reaction. RESULTS: As a result of the statistical analysis, a significant difference was found between the groups in terms of inflammation levels on the 2nd and 5th days (p<0.05). In the intragroup evaluations, the rate of severe inflammation on the 2nd day in the diabetes+chitosan group was found to be statistically significantly higher than the 5th day (p<0.05). While there was no statistically significant difference between the groups in terms of fibrosis levels on the 2nd day (p>0.05), a statistically significant difference was found in terms of fibrosis levels on the 5th day (p<0.05). CONCLUSION: It was observed that chitosan did not cause foreign body reaction in any of the groups on the 2nd and 5th days.