A 48-year-old male patient presented to the Department of Endodontics for evaluation of right first permanent molar, which had received non-surgical root canal treatment two years ago and was restored with core material. The presenting symptoms included swelling in the buccal vestibule and pain overnight. Clinical examination demonstrated that the mandibular right first molar was sensitive to percussion and also showed fluctuant swelling in the vestibule proximal to the molar and mild mobility. Radiographic examination revealed a poor quality obturation of the mesial and distal root, distal root resorption, extensive periapical and furcation radiolucency and bone loss. A diagnosis of acute periapical abscess of the mandibular right first molar was made. Tooth was treated non-surgically by the manual application of MTA in the root canal. Follow-up evaluation was performed at one year after the treatment. Clinically, treatment was considered successful due to the absence of clinical signs, symptoms and radiographic appearance with substantial reduction (more than 50%) in the diameter of the periapical radiolucency. Mineral trioxide aggregate monoblock obturation technique appears to be a valid technique to obtain periradicular healing in re-treatment of previously root canal treated teeth with periapical lesion.