The aneurysmal bone cyst is a very infrequent, benign bone lesion in children which rarely can be found at the craniofacial skeleton. Here, we describe a case presenting in the mandible as an acute swelling of the cheek, which was initially misdiagnosed as osteomyelitis resulting in a delay to definitive surgical treatment. The cause of misleading diagnosis is often owing to the rapid growth of the lesion, sometimes associated with painful soft tissue swelling indicating an infectious origin or a malignant tumor. Magnetic resonance imaging revealed the classic characteristics of aneurysmal bone cyst with severe destruction of the mandible. Therefore, curative tumor embolization and complete surgical excision was successfully performed. The aneurysmal bone cyst is a curable condition by radical excision, although relapse may occur when only incomplete excision is obtained. Therefore, aneurysmal bone cyst should be considered early when children present with unusual, rapid-growing neoformations of the extremities or the facial region.