External cervical resorption (ECR) is the loss of dental hard tissue as a result of odontoclastic action; it usually begins on the cervical region of the root surface of the teeth. The etiology, predisposing factors, diagnosis, and management of ECR have been reviewed here. Effective management and appropriate treatment can only be carried out if the true nature and exact location of the ECR lesion are known. This paper reports on the management of a case of external cervical root resorption (ECRR), which involved root canal treatment and removal of the resorbing area of the affected tooth as well as filling the resorbed area with mineral trioxide aggregate (MTA) and resin-modified glass ionomer filling material (RMGIC). The defect was filled with bone graft material and guided tissue regeneration (GTR) membrane. This case highlights the importance of using MTA and successful management of cervical resorption with a stable uneventful clinical recovery.