Internal resorption is a clinically asymptomatic condition commonly detected by routine radi-ographic evaluation. The use of mineral trioxide aggregate (MTA) is a conservative approach to repair lesions with periodontal communication. This case report presents a perforating internal re-sorptive defect at the maxillary lateral incisor repaired by MTA. During the endodontic treatment, calcium hydroxide was placed as a temporary dressing. After this period, the root canal space was filled with gutta-percha. After the treatment, a perforation on the palatal side was observed by the cone-beam computed tomography (CBCT). Surgical treatment including removal of granulation tissue and MTA displacement was done. The clinical findings and periapical radiographs indicated success of treatment until 6 months of follow-up.