The infundibular keratinizing acanthoma (IKA) is a rare epithelial benign keratin-containing neoplasm of hair follicles. The purpose of this study was to evaluate the defining histopathologic architecture of IKA. A typical IKA consisted of a keratin-filled crypt in the dermis and subcutis that opened to the skin surface. Most of this tumor occurred on the back, neck, head, and the shoulders. Microscopically, the dermal nodules were focally contiguous in both the dermis and subcutis. Furthermore, most histological lesions are consistent with a simple or multiloculated cyst filled with keratin and lined by a wall of stratified squamous epithelium; keratin appears as a concentric lamellar mass, with a keratotic pearly aspect. Histological examination of the cutaneous lesions revealed that the growths were comprised of IKA. IKA of man and dog were compared, and it was concluded that although they are similar in many respects, they are not identical entities. To the best of our knowledge, this is the first report on the prevalence of IKAs among the population of owned dogs in Iran.