Objectives/Hypothesis: Surgical treatment of inverted papilloma (IP) of the sphenoid sinus is complicated by close proximity to vital structures of the skull base. Identifying the site of tumor attachment and achieving complete removal can be challenging compared to IP at other sites. The objective of this study is to illustrate the clinical presentation, management, and risk factors for tumor recurrence for sphenoid IP. Study Design: Retrospective study. Methods: A multi-institutional, retrospective review of endoscopic resections of IP based within the sphenoid sinus was performed from 1996 to 2014. Demographic and tumor data, operative notes, complications, and recurrence rates were collected. Statistical analysis was performed to identify risk factors for tumor recurrence. Results: Forty-eight patients (31 males, 17 females) were identified. Mean age was 57 years, with a median follow-up of 13.6 months (range 6.8-36). Rate of tumor recurrence was 14.6%, with median time to recurrence of 13.1 months. Patients with dysplasia/carcinoma in situ (CIS) had a 3.6 greater rate of recurrence (RR) compared to patients with no dysplasia, approaching significance (RR=3.6; P=0.08). Patients with IP attachment sites overlying the optic nerve or carotid artery had a 4.76 greater rate of recurrence compared to other sites (RR=4.76; P=0.073). Conclusion: Sphenoid sinus IP is associated with a 14.6% rate of recurrence after surgery. Potential risk factors for tumor recurrence identified in this study include attachment sites over the optic nerve and carotid artery or evidence of dysplasia or CIS. Close follow-up in the postoperative period is essential for these patients to monitor for tumor recurrence.