Background: The Draf III procedure is an effective endoscopic approach to the treatment of frontal sinus disorders, but has a significant restenosis rate. The objective of the current study is to assess long-term success of the Draf III mucosal grafting technique. Methods: Patients undergoing Draf III with mucosal grafting technique were prospectively enrolled. Demographics, indication for surgery, anterior-posterior (AP) diameter of frontal ostium, and complications were recorded. Failure was defined a priori as closure ≥50% of the intraoperative AP diameter at last clinical follow-up. Results: Ninety-six patients requiring Draf III with mucosal grafting were enrolled, 67 of which (average age 54 years; range, 15-84 years) had at least 1 year of follow-up (average 34 months; range, 12-85 months) and were included in the analysis. Reasons for the procedure included chronic rhinosinusitis with frontal ostium stenosis (n = 37), tumor (n = 26), and cerebrospinal fluid leak (n = 4). Average preoperative Lund-Mackay score was 13.9 ± 7.8. Average intraoperative AP diameter was 11.0 ± 1.9 mm. The procedure was highly effective with 97% (65/67) of patients maintaining a patent frontal sinus ostium (>50% intraoperative AP diameter) for the duration of follow-up (average postoperative diameter 9.9 ± 2.2 mm). However, the 2 Draf III failures remained patent, did not need further intervention, and were considered clinically successful. Three patients required reoperation for reasons unrelated to closure of the Draf III. Conclusion: Common causes of failure following Draf III procedures include osteoneogenesis and stenosis. This study provides long-term data demonstrating excellent outcomes using the mucosal grafting technique.