© 2021 S. Karger AG, Basel.Introduction: Tegmen defect (TD) has a potential of intracranial spread of middle ear infection, meningoencephalic herniation (MEH), and cerebrospinal fluid leakage (CSFL). Especially the defects >1 cm with MEH or CSFL are generally repaired via the classical middle fossa or minicraniotomy technique. The aim of this study was to show the efficiency of the intracranial, extradural placement of the septal cartilage graft in the closure of the TD larger than 1 cm via the transmastoid (TM) approach. Methods: The demographic, preoperative, intraoperative, and postoperative data of 11 patients with chronic otitis media (COM) who had TD larger than 1 cm were reviewed retrospectively. Hospitalization time and hearing preservation with respect to MEH or CSFL were analyzed. Results: The most common etiology of TD was cholesteatoma (82%), and 91% of the patients had multiple COM surgery history. The mean TD size was 15.4 (10-25) mm. Fifty-five percent of the patients presented with either MEH or CSFL. The mean follow-up of the patients was 22.5 (8-42) months. There was no significant difference between preoperative and postoperative mean bone conduction thresholds. Mean hospitalization time was 5.2 (3-10) days. There was no significant difference in the hospitalization time between patients with MEH or CSFL and without MEH or CSFL. Neither recurrence nor graft infection was encountered. Conclusion: Extradural grafting with the septal cartilage in the large TD up to 25 mm can be repaired efficiently via the TM approach without application of a lumbar drainage.