Resection of the cavernous sinus (CS) lesions has been a surgical challenge because the anatomy of the CS presents a high grade of complexity. This report describes the feasibility of the purely endoscopic endonasal approach to the CS. Twenty-five patients with intracavernous sinus tumors were treated with a purely endoscopic endonasal approach. The indications, efficacy, surgical techniques, and complications of this approach were discussed. Gross total resection occurred in 19 cases (76%), subtotal resection occurred in 2 cases (8%), and partial resection occurred in 4 cases (16%) including pituitary adenoma in 10 cases (total 70%; subtotal 10%; partial 20%), meningioma in 6 cases (total 66.6%; subtotal 16.7%, partial 16.7%), schwannoma in 5 cases (100%, total 5), malignant tumor in 4 cases (total 75%; subtotal 25%). All patients experienced resolution or improvement of symptoms. No patient experienced intraoperative complication and new neurological deficit. Only 1 case of postoperative cerebrospinal fluid leakage repaired via endoscopic endonasal approach on the 14th day after the surgery. The purely endoscopic endonasal approach to the CS in appropriately evaluated patients can be used to address a wide variety of benign and malignant tumor pathology with favorable outcomes and a low incidence of complications.