Background: Interferon α-2b (IFNα2b) was recently shown to be effective as an alternative therapy for conjunctival intraepithelial neoplasia (CIN). Herein, we report our successful management of CIN by the use of IFNα2b.Case: A 73-year-old woman presented with a complaint of irritation due to a tumorous lesion in her left eye. Slit-lamp microscope examination revealed a tumorous lesion involving the bulbar and palpebral conjunctiva as well as the limbus, from the 3-o'clock position to the 8-o'clock position. She had already undergone cryotherapy in the same eye in another hospital, twice for a lesion on the lower tarsal conjunctiva and once for a lesion on the upper tarsal conjunctiva. The histological diagnosis had been CIN.Observations: In treating this patient, IFNα2b was injected subconjunctivally twice and also applied as eye drops for 12 weeks. Two weeks after the initial treatment, the tumorous lesion disappeared. During a 1-year follow-up period, no recurrence was noted.Conclusion: Topical and subconjunctival IFNα2b is a valuable treatment option for CIN.