The impact of goldfish exposure for 96 h to herbicide Gesagard 500 FW at concentrations 0.2, 1, or 5 mg L −1 (corresponding to 0.1, 0.5 or 2.5 mg L -1 of effective compound prometryn) on the hematological profile of blood and biochemical parameters of plasma and liver was studied. Fish exposure to low concentration of the herbicide (0.2 mg L -1 ) slightly decreased liver glycogen and plasma lactate levels. Plasma glucose levels rose by 27% in goldfish exposed to 1 mg L -1 Gesagard. The activity of lactate dehydrogenase decreased by 63% and 36% in plasma of fish exposed to herbicide at concentrations 1 and 5 mg L -1 , respectively, but was not affected in liver. Goldfish exposure to the highest concentration of Gesagard (5 mg L -1 ) decreased hematocrit by 23% and increased monocyte count by 57%, and elevated triacylglycerol level by 91% in plasma. Overall, the results indicate that acute exposure to Gesagard induced minor changes in the hematological and biochemical parameters of goldfish, suggesting that disruptions of these parameters may provide early warning signs that could be useful for assessing acute or sublethal toxic effects of pesticides on aquatic species.