Purpose <p>To assess whether applying topical dexpanthenol to the oral commissures immediately before surgery reduces the incidence of postoperative angular cheilitis in children undergoing adenotonsillectomy.</p> Methods <p>A total of 101 pediatric patients who underwent adenotonsillectomy were included in this study. Patients were randomly divided into two groups based on whether or not dexpanthenol was applied to the lip corners immediately before surgery. Postoperative pain and presence of angular cheilitis were assessed and compared between the groups on the postoperative first day and first week.</p> Results <p>In the study group, only 9.8% (<i>n</i> = 5) of patients exhibited angular cheilitis on postoperative first day, whereas in the control group angular cheilitis incidence was 44% (<i>n</i> = 22) and the difference between two groups was statistically significant (<i>p</i> &lt; 0.001). On postoperative first week examination, 3.9% (<i>n</i> = 2) of patients in the study group and 10% (<i>n</i> = 5) of patients in the control group exhibited angular cheilitis and the difference between the two groups was not significant (<i>p</i> &gt; 0.05). Logistic regression analysis revealed that topical dexpanthenol application significantly reduced the odds of developing angular cheilitis on the first postoperative day (Odds Ratio: 0.14; 95% CI: 0.05–0.41; <i>p</i> &lt; 0.001). Pain scores recorded on postoperative first day and first week did not show significant difference between the two groups (<i>p</i> &gt; 0.05).</p> Conclusions <p>A single application of topical dexpanthenol immediately before surgery is a simple intervention and significantly reduces the early incidence of postoperative angular cheilitis without affecting postoperative pain scores in pediatric adenotonsillectomy patients.</p> Trial registration <p>ClinicalTrials.gov Identifier: NCT07002632, registered on 25 May 2025 (retrospectively registered).</p>