BACKGROUND: Tobacco (Nicotiana tobaccum) is a plant with piscicidal and fertilizing properties. OBJECTIVES: In this study the effect of different concentrations (0.1, 1, 10 and 100mg/l) of hydro-alcoholic extracts of tobacco has been examined on different tissues of Rainbow trout. METHODS: Samples from liver, kidney and gill of Rainbow trout were stained with hematoxylin and eosin and studied under light microscopy. RESULTS: Various histopathological lesions were observed in the liver of Rainbow trout exposed to different concentrations of tobacco. The results showed that with increase in concentrations of tobacco up to 10 and 100mg/l, bloodshed increased and hepatocytes lost their continuity and showed discontinuity mood. Lamellar aneurysm, bleeding and leukocytes infiltration, clubbing at the end of the lamellae, hyperplasia of secondary lamellar epithelium, epithelial lifting of secondary lamellae and creating an edematous space, lamellar shortening, vacuolation and lamellar fusion were the more abundant branchial lesions after exposure to tobacco. Separating the epithelium from basement membrane, hypertrophy, glomerular capillary dilation and tubular degeneration were observed in renal tissues in all treatments. At higher concentrations of tobacco (10 and 100mg/l), renal tubular necrosis was also observed. According to the results liver of rainbow trout showed a few histopathological alteration following exposure to tobacco extracts. Unlike the liver, gills of rainbow trout due to direct contact with pollutants showed more lesions. CONCLUSIONS: Tobacco extract has more pathological effects on gills in comparison with liver and kidney of Rainbow trout due to direct contact with the dissolved pollutant.