ABSTRACT. In the last few years, the adoption of Teleosts as bioindicators of anthropogenic impact on aquatic environments has become popular. Fish are excellent bioindicators of aquatic ecosystem health because of their high sensitivity to environmental changes. It has been widely shown that exposure to genotoxic agents can cause important severe alterations and damages at different levels of structural complexity: the onset of micronucleous (MN) and nuclear abnormalities (NA) are the result of molecular damages induced by genotoxic agents, demonstrating their effectiveness in detecting the presence of genotoxic agents. Compared with other cytogenetic methods, the MN test is the most widely used test for aquatic species as it does not involve cell cultures, it is independent from the number of species’ chromosomes, it is fast and easy, and the micronucleaous identification at the microscope is quite simple. This study aimed to assess the damage caused by genotoxic agents in aquatic environments, based on the presence of micronucleous and nuclear abnormalities in erythrocytes of the blenny Parablennius sanguinolentus (Pallas, 1814), collected in two sites along the eastern coast of Sicily (Italy). Such a species was considered as a valid bioindicator due to its biological features and its occurrence in the sites object of this study.