Middle ear osteoma is an extremely rare benign tumor of the middle ear. Due to its very slow growth rate and benign nature, osteoma of the middle ear can be found incidentally without causing any symptoms. The most common clinical signs are conductive hearing loss, the sense of fullness in the ear, tinnitus, and otorrhea. Small-sized osteomas can be misdiagnosed as otosclerosis without showing any signs other than conductive hearing loss. When the mass becomes very large, and symptoms caused by the tumor increase, treatment also becomes difficult. In this paper, we report a case of middle ear osteoma causing conductive hearing loss and effusion due to the effect of pressure on the middle ear ossicles and the Eustachian tube. We also present a review of the pertinent literature.