The treatment of qualitative olfactory disease is challenging. We aimed to treat parosmia using a new minimally invasive surgical technique-the olfactory cleft blocking technique-by preventing odorants from reaching the olfactory epithelium. A novel surgical procedure for blocking the anterior and inferior openings of the olfactory cleft was accomplished in a patient with unilateral persistent peripheral parosmia. The HRCT and endoscopy were performed preoperatively and postoperatively to evaluate the anatomical structure of the olfactory cleft. The T&T olfactometer was used to assess the preoperative and postoperative olfactory function. After surgery, the pa-tient's parosmia disappeared. Endoscopic examination and CT scan showed complete obstruction of the anterior and inferior portions of the olfactory cleft. No recurrence was reported during a 2-year follow-up. No surgical complications were reported except olfactory loss in the opera-tive nostril. For patients with long-term unilateral peripheral olfactory dysfunction, the olfactory cleft blocking technique seems a novel, simple, safe and effective treatment. Further studies are required with a larger number of patients in order to access success rate. (c) 2020 Oto-Rhino-Laryngological Society of Japan Inc. Published by Elsevier B.V. All rights reserved.