Osteoid osteomas are benign osseous lesions. They have seldom been described in the otolaryngology literature, and they are extremely rare in the ethmoid sinuses. We report a new case of osteoid osteoma of the ethmoid sinus in a 15-year-old girl. The workup consisted of computed tomography. Treatment involved local excision via an external ethmoidectomy approach. The diagnosis was based on histopathologic examination.