Intradiploic epidermoid cyst is a benign lesion that is derived from the ectodermal cells of the cranium. It is a rare tumor, representing less than 1% of all primary intracranial tumors. It can be located in any part of the skull, but frontal and parietal bones are the most common sites for the cysts. It occurs from the first to the seventh decade of life. Because it is a slowly growing tumor, it is usually discovered incidentally and may remain asymptomatic for many years. Rarely, it grows intracranially to produce brain compression or undergo malignant change. For treatment, it is important to completely remove the capsule of the cysts to avoid recurrence. I describe a 25-year-old man with an intradiploic epidermoid cyst of the temporal bone, who underwent tumor removal and simple mastoidectomy. I also describe the unique radiologic findings of my case, which differed from those of cholesteatoma.