The authors report a novel treatment of a case of type I laryngeal cleft diagnosed in an adult. They describe a technique of endoscopic obliteration of the posterior commissure defect. Initially, a test implant of starch and adrenaline was used, followed by permanent staged injections of Bioplastique™ to the posterior commissure. This rare congenital anomaly usually presents in childhood but late presentation should be considered when adults present with lifelong dysphonia especially when associated with gastro-oesophageal reflux disease.