Preeruptive intracoronal radiolucencies (PEIRs) are mostly incidentally found by routine radiographic examination of unerupted teeth. PEIRs are classified into two types according to the nature of the lesion: progressive and nonprogressive. A case report of a 17-year-old boy with a nonprogressive PEIR on the permanent mandibular left second molar is presented. The lesion was initially detected on an unerupted tooth at age eight years, eight months. It was clinically and radiographically assessed yearly. Cone beam computed tomography (CBCT) was used to evaluate the lesion's size and location when the patient was 11 and 14 years old. The assessments confirmed that the lesion was nonprogressive and had no connection to the pulp or oral cavity. Due to the static nature of the detected PEIR during the nine-year follow-up period, the patient's low caries-risk status, and high patient and parental cooperation in periodic dental care, it was decided to place resin sealant on the affected tooth and monitor the lesion without any operative treatment.