Immunoglobulin G4-related disease (IgG4-RD) is a chronic inflammatory disease involving multiple organs. Some studies have reported otological manifestations of IgG4-RD, although most studies describe involvement of the middle ear, and reports on inner ear manifestations are limited. Here, we describe a case of a 30-year-old man with IgG4-RD involving the inner ear. This case demonstrated that IgG4-RD affected the inner ear and caused cochlear ossification. Cochlear implants may be considered for milder cases, and hormone and immunosuppressive therapy may control disease progression. © The Author(s) 2020.