The purpose of this case report was describe the management of impacted and dilacerated mandibular secondary primary molar with cystic formation associated with odontoma. A four-year-old male patient was presented unerupted mandibular left secondary primary molar. Radiographic examination revealed radiopaque mass on left posterior mandible, an impacted and dilacerated mandibular secondary primary molar, and a well defined osteolytic lesion surrounding crown of the impacted tooth. Under local anesthesia, the patient was treated by surgical removal of the odontoma and marsupialization of the cystic cavity. After 14 months, the secondary primary molar had erupted and there was no recurrence.