In the context of the global increase in pesticide applications, aquatic animals are constantly subjected to their action in natural reservoirs. Our research sought to determine the molecular and biochemical effects of an environmental exposure to commonly used chloro-s-triazine herbicide terbuthylazine and organophosphate insecticide malathion on zebrafish. To this aim, mature zebrafish were exposed to 2 and 30 µg L−1 terbuthylazine and 5 and 50 µg L−1 malathion alone and in combination for 14 days. Following exposure, induction of reactive oxygen and nitrogen species, lipid peroxidation, and protein carbonylation in the liver of treated zebrafish have been registered. Aside from the accumulation of oxidative lesions, a decrease in antioxidants and succinate dehydrogenase activity, an increase in oxidized glutathione, and enhanced apoptosis via Caspase-3 and BAX overexpression (in the case of terbuthylazine) were observed. Furthermore, terbuthylazine and malathion induced mitochondrial swelling and lactate dehydrogenase leakage in a concentrationdependent manner. Significant upregulation of ubiquitin expression and increasing cathepsin D activity were characteristics that appeared only upon terbuthylazine exposure, whereas induction of IgM was identified as the specific characteristic of malathion toxicity. Pesticides in the studied concentration didn’t provoke significant alterations in the hypothalamic-pituitary-thyroid axis in zebrafish. Co-exposure increased adverse effects of individual pesticides to zebrafish. This study should improve understanding of the mechanisms of pesticide toxicity that leads to fish impairment and biodiversity decline, as well as emphasize the importance of paying attention to pesticide traces in the environment and fish, which can have devastating effects on biota even at low concentrations.