-OBJECTIVE: The endoscopic endonasal approach (EEA) has been applied in the treatment of olfactory neuroblastoma (ONB). However, there is a lack of research examining the impact of EEA on locally advanced ONB. This study assessed the outcomes of EEA in patients with locally advanced ONB and its impact on the quality of life (QOL). METHODS: We retrospectively reviewed patients with Kadish stage C ONB who underwent EEA between December 2004 and October 2019 and assessed demographic data, histopathologic grade, the extent of resection, postoperative complications, and outcomes. Preoperative and postoperative QOL was assessed using the Sino-Nasal Outcome Test. RESULTS: Twenty-six patients (18 men, 8 women; aged 26-79 years) were enrolled, with 12 cases of Hyams grade II and III and 1 case of grade I and IV each. In total, 25 patients received radiotherapy and 16 patients received chemotherapy, of whom 11 received preoperative neoadjuvant chemotherapy. Postoperative nasal bleeding was observed in 2 patients. The follow-up ranged from 8 to 124 months (median, 42.3 months). The 1-year and 5-year overall survival were 96.2% and 84.8%, respectively. The 1-year and 5-year disease-free survival were 76.9% each. The analysis of the postoperative Sino-Nasal Outcome Test scores showed significant improvement in certain psychological and sleep-associated domains, compared with the preoperative scores. CONCLUSIONS: Our results showed that pure EEA followed by radiotherapy offered excellent outcomes in the management of selected patients with locally advanced ONB. The postoperative QOL was significantly improved. More research is required on neoadjuvant chemotherapy to establish its role.