Syringomyelia (SM) is a disorder in which a cyst forms within the spinal cord. This cyst, called a syrinx, expands and elongates over time, destroying the center of the cord. Horner syndrome is an infrequent illness caused by a lesion of the cervical sympathetic nerve fiber. Its clinical features are facial anhidrosis, ptosis, miosis, and hypochromia iridis of the affected side. A full-term male newborn infant was admitted with weakness in bilateral upper extremities and narrowing of the palpebral fissure on the right side. Ophthalmologic examination revealed a smaller right pupil. Muscle power in bilateral upper limbs was 1/5. Chest X-ray and cranial magnetic resonance imaging were normal. Magnetic resonance imaging of the cervicothoracic spine showed SM at C4-T2 level. Electromyographic examination revealed bilateral brachial plexus palsy. The diagnosis was of brachial plexus palsy and congenital Homer syndrome due to congenital cervicothoracic SM. According to our best knowledge, this association has not been reported in the literature. (C) 2009 Elsevier B.V. All rights reserved.