Crude oil is enriched in polycyclic aromatic hydrocarbons (PAHs). Many PAH analogs have proved to potentially damage DNA. DNA damage can be assessed using various biomarkers to find out the degree of genotoxicity of pollutants following in vitro exposure. In this research the comet assay and micronucleus (MN) test were used to detect DNA damages and cytogenetic changes following crude oil exposure. For this purpose, freshwater bivalve mollusks (Anodonta cygnea) were exposed for ten days to 0.25, 0.5 and 1.0 ppm of crude oil. For the comet assay and for the MN test, hemolymph and gill cells of mussels were sampled respectively. Statistically, significant increase of DNA damage and micronuclei were found with 0.25, 0.5 and 1.0 ppm of crude oil. This study was performed to ascertain that A. cygnea is a good bioindicator of pollutants in aquatic environments; also identified hemolymph and gill of A.cygnea are most effective and practical tissues for genotoxicity studies.