A rare case of aneurysmal bone cyst (ABC) located in the coronoid process of the mandible in a 12-year-old girl is presented. Treatment consisted of excision of the lesion through preauricular, submandibular and intraoral approach. An access osteotomy distal to second molar region was required to gain access to medial side of the coronoid process. To our knowledge, this is the third case of an aneurysmal bone cyst of the coronoid process of mandible. While examining a patient with a large expansile intrabony jaw cavity with thin peripheral bone, which is filled with blood without presence of bruit, thrills and pulse pressure, the diagnosis of aneurysmal bone cyst should be on top of the differential diagnosis list. Seventy-four to eighty-five percent of aneurysmal bone cysts of jaws occur in 10-20 years age group. Therefore, a pediatric dentist may be the first person to see such a lesion.