The shorten lingual frenulum is the most common congenital defect of the tongue, in which the frenulum is incorrectly tied to the bottom of the oral cavity. This type of anatomy significantly reduces normal tongue movement and leads to several abnormalities, like problems with breast feeding, speech impediments, malocclusion, functional disorders, dyspnea, dysarthria, social problems. We can distinguish several methods of the treatment of this abnormality, both conservative (like exercise of the muscles of the tongue or appropriate speech therapy) and surgical, most commonly frenulotomy. Technically, the procedure of the frenulotomy is quite easy to perform, but requires proper acquaintance with the anatomy of this region determining the potential extent of the procedure and thorough investigation of our patient in order to avoid possible serious, sometimes even life-threatening, complications. In our article we present a case of a 16-year-old patient treated chronically due to malocclusion in a private dental center that was qualified for the procedure of frenulotomy after a speech therapy consultation. The procedure was performed under local anesthesia and unfortunately complicated by massive bleeding from the mouth.