Background: External cervical resorption (ECR) is one of the subclassifications of external root resorption. In most cases it is not evident and asymptomatic before the involvement of the pulp. The etiology of ECR is still unclear. Case presentation: This paper reports a case of ECR in the mandibular right first molar of a 24-year-old patient who presented with an asymptomatic pink tooth. A two-dimensional radiograph and CBCT showed cervical resorption penetrating at the cementoenamel junction level from the mesio-lingual aspect. It approximates the pulp horn coronally within the lingual dentinal wall. Discussion: The treatment of the case involved debridement of the resorptive defect and mineral trioxide aggregate (MTA) was applied as a direct pulp capping, glass ionomer as a base, and the tooth restored using resin composite restoration. After 6-months of follow-up, the radiographic examination showed healthy bone and periodontal structures with no evidence of periapical pathology. Conclusion: ECR is an aggressive and invasive lesion that acts silently, requiring early diagnosis and treatment for a successful outcome. The lesion size, location, and accessibility are the main factors affecting successful treatment of ECR.