Extreme weather events are increasing with global climate change and are of concern to aquaculture and fisheries scientists and producers. Temperature is a key environmental factor determining fish growth and metabolism. Hence, the following study was conducted to investigate the effect of extreme temperature events on the growth and hematological parameters of European seabass, Dicentrarchus labrax. Fish were exposed to 8 °C, 16 °C, 24 °C, 32 °C for 30 days mimicking temperature extreme events. Growth performance measured as final weight, weight gain, specific growth rate, survival rate, and temperature growth coefficient was significantly impaired (p < .05) at 8 °C and 32 °C compared to 16 °C and 24 °C. Hepatosomatic index (HIS), viscera somatic index (VSI), intestine somatic index (ISI) and spleen somatic index (SSI) were significantly (p < .05) lower for fish at 8 °C and 32 °C. White blood cell (WBC), plasma triglycerides and lactate were significantly (p < .05) increased at 8 °C and 32 °C, while plasma glucose, total protein and red blood cell (RBC) exhibited the inverse trend. Erythrocytes cellular abnormalities (ECA) and Erythrocyte nuclear abnormalities (ENA) frequencies were found to be significantly (p < .05) higher for fish reared at 8 °C and 32 °C. Among treatments, both ECA and ENA frequencies were found to be higher at day 10 compared to day 20 and 30. European seabass clearly exhibit significant physiological alterations and marked performance reduction during extreme temperatures of 8 °C and 32 °C, many of which are not compensated for by physiological adaptation. Results are discussed in terms of potential production impacts and mitigation options for European seabass culture during extreme temperature events.