As being the main energy source that is needed for all of the industrial processes, crude oil is evaluated as a widely investigated ecotoxicant. In order to identify the effects of crude oil on the skin of teleosts, Poecilia sphenops specimens were exposed to three different concentration of soluble part of crude oil (10%, 20%, 40%) at four different exposure time (24, 48, 72, 96 h); and the histopathological changes were reported. A slight epidermis corrosion and melanophore aggregation in dermis were observed at low concentration and short exposure time. As estimated, the striking effects of the crude oil; such as dermis disintegration, necrotic areas and fibrosis in subcutaneous muscle layer; were extended prominently in parallel with increasing concentrations and exposure time.