The purpose of treating a furcal perforation is to seal the artificial communication between the endodontic space and the periradicular tissue to prevent alveolar bone resorption and damage to the periodontal ligament. These complications are not infrequent in cases of large furcal and/or old perforations, which have a worse prognosis than recent, small, coronal and apical perforations. Mineral trioxide aggregate (MTA) is widely used to seal perforations, because of its biocompatibility and sealability. This case report describes the management of a large furcal perforation in a mandibular first molar. Although most of the pulpal floor was destroyed and the roots were damaged, an attempt was made to repair the defect and restore the tooth. The perforation was cleaned with saline solution and ultrasonic tips. Finally, the perforation was sealed with MTA and the tooth restored coronally. A 21-month recall showed no evidence of periodontal breakdown, no symptoms, and complete healing of the surrounding periodontal tissue. Keywords: biocompatibility, furcal perforation, MTA, root perforation, wound healing