The harmful effects of ultraviolet radiation on aquatic animals, due to ozone layer reduction, have been long studied in recent years. Exposure of Rainbow Trout larvae (Oncorhynchus mykiss) to Ultraviolet-B radiation (UV-B) at different doses (68.75 µw/cm2 and 94.83 µw/cm2 as the minimum and maximum dose of UV-B in natural environment respectively) for 15 minutes once a day in dark condition in comparison to control group (without any solar or UV) showed a wide variety of body abnormalities and eye damages. Body curvature, yolk sac edema, fin blistering, dwarfism, eye and head abnormalities as morphological malformations were revealed during the experiment, none of the malformations were observed in control group. Histopathological changes in retina such as irregular and discontinues pigmented epithelium, necrosis of photoreceptors and degeneration of nucleus layers confirmed the destructive effects of UV-B radiation in the eyes of Rainbow Trout. Such changes in larvae can be valid as bio-indicator for pollution and UV radiation and also introduce fishes as model for toxicological studies.