Coronoid hyperplasia is a rare entity of unknown etiology due to increased and persistent bone growth that has been associated with trauma, inflammation, hormonal influence and hypervascularization. A case of coronoid hyperplasia in a pediatric patient with restriction in mandibular movements and an absence of painful symptoms initially misdiagnosed as a functional temporomandibularjoint (TMJ) abnormality is presented. Causative factors and management strategies are emphasized to enhance the recognition and understanding of mandibular hypomobilities.