Meningioma is the most common intracranial benign tumor in adults. Hyperostosis accompanies about 4.5% of meningiomas. The authors report a rare case of hyperostotic meningioma that may have been misdiagnosed as giant osteoma.A 42-year male visited our clinic due to an egg-sized, hard mass on his left forehead. The mass suspected to be giant osteoma was about 4.2 × 4.0 cm sized, hard, non-movable, and non-tender. But based on radiologic findings, the mass was diagnosed as meningioma with extensive hyperostosis.Without neurologic symptoms, the diagnosis of meningioma associated with hyperostosis can be challenging and be misdiagnosed as fibrous dysplasia and osteoma by simple examination without enhanced CT and MRI.Therefore, although osseous lesions are strongly suspected to be osteomas, surgeons should consider other diagnoses, and if necessary, use contrast enhanced CT or MRI to differentiate these bony lesions.