Immunohistochemistry can be an important method in diagnosis, investigation, and determining the behavior and pathogenesis of oral tumors. Immunohistochemistry protocols were formed using antibodies tagged with chromogens to identify particular markers. In these protocols, antigen-antibody reactions occur using nonfluorescent chromogens and then are analyzed in an optical microscope. Subspecialties of pathology like in that of oncologic pathology, neuropathology, and hematopathology, gradual increase in need of IHC can be observed as time goes by. As specific diagnostic markers can be present extensively in cells of a particular neoplasm and not in other tumors thus these markers can be used to find out the cellular lineage and histogenic origin of different neoplasms. This paper focuses mainly on the Applications of Immunohistochemistry in Oral Pathology.