This case report describes endodontic treatment of a large periradicular lesion in a 46 year old male with spontaneous intermittent pain in relation to his lower left back tooth region presented into private practice, accompanied with a restoration, which is tender on percussion and poorly root treated with incomplete obturation, missed mesiolingual canal and mesial root perforation. Re-root canal treatment had been done on involved tooth along with perforation closure followed by permanent coronal restoration in multiple appointments. Postoperative examination during further follow-ups showed complete healing of periradicular lesion. The proper diagnosis of apical periodontitis and appropriate treatment plan of infected root canal system of previously treated tooth allowed complete healing of this lesion without endodontic surgery. Key words: Peri-radicular lesion