For osteoblastoma, with its predilection for the spinal column and appendicular skeleton, the skull is an unusual site, and paranasal sinus involvement is very rare. Herein, we report on a case in which the disease was located within the sphenoid bone. To the best of our knowledge, this is the 4th reported case of osteoblastoma with a sphenoid origin (1). We report an osteoblastoma of the sphenoid sinus in a 12-year-old girl who presented with exophthalmos. Computed tomography (CT) demonstrated an expansile lesion of the sphenoid which caused the orbital contents to be compressed and deviated to the right. In the magnetic resonance imaging scan, the lesion was found to invade the cranial base in the frontal and temporal region, approximating to the cavernous sinus and internal carotid artery on the right. Bilateral fronto-orbital craniotomy was performed. Histologically, the lesion was composed of proliferating osteoblasts along with vascular stroma. The tumor was described as an aggressive osteoblastoma. In the follow-up CT four months later, a pathological mass was observed in the area of the nasal septum, and a signal void was present on all sequences in the densely sclerotic areas. A second resection was performed. The patient has been disease-free for 61 months. Herein, we present the diagnosis and management of this unusual lesion. The histopathology and the imaging characteristics are shown.