Mitomycin C is part of the mitomycin group of antibiotics and has found use in medicine in the treatment of various cancers, including those of the head and neck. In recent years, it has gained popularity as a topical treatment to prevent scar formation in the larynx and choanae in paediatric and adult inflammatory processes. Also, this alkylating agent is potentially a potent carcinogen. We report the first case in the world literature of laryngeal carcinoma in a non-smoking adult, which may have been induced by topical mitomycin C application to a glottic web. We discuss the mechanism of action of this drug, and we advise caution on its use for benign laryngeal pathologies.