Leiomyoma is a benign tumor of smooth muscle origin that rarely occurs in the oral cavity. Of the 118 cases occurring in the oral cavity described since 1884, only five involved the mandible. This is a case of an intraosseous leiomyoma in a 9-year old child, who presented to our attention with a firm intra-oral mass, involving the angle and the posterior portion of the left mandibular body. The patient was treated with local incision alone, preserving the permanent dental germs and the left inferior alveolar nerve. He remained disease free with regular follow-up for 40 months.