Background​​ <p>Surgical extraction of impacted mandibular third molars is frequently associated with postoperative complications. This study aimed to evaluate the efficacy of mucosal fenestration drainage—a novel technique—in improving postoperative outcomes following such extractions.</p> ​​Methods​​ <p>Between September 2022 and September 2023, patients requiring extraction of impacted mandibular third molars at our hospital were enrolled. Those with fully impacted teeth were randomly assigned to either a suture group (primary wound closure) or a drainage group (fenestration drainage in the posterior molar region). Patients with partially impacted teeth were included as a natural group. Postoperative reactions and complications were assessed and compared.</p> ​​Results​​​​ <p>A total of 120 patients were included (40 per group). Postoperative swelling was significantly reduced in the drainage group compared with the suture group on postoperative day 2. The natural group, which consisted of partially impacted teeth and was included according to impaction status, showed relatively lower swelling scores during the early postoperative period; however, this finding should be interpreted as clinical reference data rather than evidence from a randomized comparator. No statistically significant differences were observed in pain, trismus, infection, lower lip hypoesthesia, or second molar discomfort.</p> ​​Conclusion​​​​ <p>Mucosal fenestration drainage confers a modest reduction in early postoperative swelling; however, its overall clinical benefit remains limited.</p> Trial registration <p>This study was registered at the Chinese Clinical Trial Registry (No.: ChiCTR2000029236) on Jan. 19th, 2020.</p>