Introduction: Chemical-mechanical preparation is of crucial importance to a successful endodontic treatment. Endodontic reintervention is indicated in cases of failure and unsuccessful outcomes. In this phase, teeth with external apical resorption require excellent care by the practitioner. In order to overcome these challenges, a biomaterial known as MTA (Mineral Trioxide Aggregate) was incorporated to the world dental market, presenting several indications, such as its use as apical plug. Objective: To report a clinical case of endodontic reintervention with indication of MTA apical plug. Case report: A Caucasian female patient reported sensitivity to palpation and presence of fistula for more than 15 days. Gingivitis and fistula were clinically observed at the bottom of the buccal sac of tooth #21. Radiographically, previous endodontic treatment was poor, presenting intraradicular metal core, external root resorption, and rarefying osteitis limited to the periapical region. Endodontic reintervention of tooth #21 was carried out. Treatment involved three visits for removal of the temporary crown, cast metal core and gutta-percha, in addition to application of intracanal dressing and the use of a MTA apical plug, as well as the application of warm gutta-percha. Thereafter, the patient was referred for definitive rehabilitating treatment. Conclusion: Clinical and radiographic follow-up after eight years revealed periapical repair and re-establishment of masticatory and esthetical functions by means of restorative procedure. Treatment was proven to be efficient in sealing the apical region of the root canal through the use of MTA apical plug; thus, showing the success and advantages of both material and therapeutic modality.