An 8-year-old girl had an orbital-adnexal lymphangioma and ipsilateral orbital and middle cranial fossa arteriovenous malformations. High-resolution magnetic resonance image scanning, orbital ultrasonography, and digital subtraction angiography were used for diagnosis and preoperative assessment. Complications related to this vascular neoplasm included amblyopia, acute hemorrhage with proptosis, exposure keratitis, cosmetic deformity, and recurrent preseptal cellulitis. The girl was treated with both embolization and orbital surgery for recurrent hemorrhage and proptosis. We postulated that the coexistence of a lymphangioma and arteriovenous malformation represents an unusual and extensive maldevelopment of vascular embryogenesis.