The main objective of this paper is to understand the importance of biochemical biomarkers in assessing marine pollution by Polychlorinated biphenyls (PCBs) and Pesticides. Methods: The oxidative stress and antioxidant response as well as ultrastructural changes of both liver and muscle tissues of Siganusrivulatus collected from El-Mex Bay as a polluted region and Marsa Matrouh as a control region far from land-based sources of pollution have been investigated by using standard methods. In general, the results cleared out that El-Mex Bay was much more polluted by polychlorinated biphenyls (PCBs) and pesticides compared to Matrouh area. The concentration range of total polychlorinated biphenyls (PCBs) and pesticides in sediment samples collected from Matrouh coast was 16.29-32.58 ng/g, dry weight and 107.62-149.11ng/g, dry weight, respectively. On contrast, the range in sediment samples collected from El- Mex Bay was 217.12-255.33 ng/g, dry weight and 663.73-778.7ng/g, dry weight, respectively. Biomarkers studies revealed that the induction of antioxidant systems in response to oxidative stress and the increase in lipid peroxidation in fish collected from the polluted area were good indicators for the pollution load" in the present study. On the meantime, the present study revealed that ultrastructural changes serve as a biomarker of stress in aquatic environment. Moreover, the results suggested that chemical pollution, on the other hand, is capable of inducing morphological alteration in liver of fish collected from polluted area.