Rapid global warming and increasingly severe heatwaves pose a serious threat to organisms in the Anthropocene. Aquatic ectotherms are especially at risk, as their body temperature generally matches that of the environment. Evolutionary adaptation is one of the few processes which might allow animal populations to better cope with these thermal challenges, yet it is rarely experimentally examined in vertebrates. Our group previously assessed the evolutionary potential for acute upper thermal tolerance by artificially selecting zebrafish on this trait, and found that evolution towards higher tolerance is possible but concerningly slow. We are currently conducting a new selection experiment using the same model species to study the evolution of thermal performance, which is distinct from acute thermal tolerance as it requires survival and resilience under chronic thermal stress. Based on growth performance in the juvenile life stage as the trait, we are selecting zebrafish to increase this performance at warm (34.5°C), control (28°C) or cold (20°C) temperatures. Starting with a genetically diverse ancestral population (6th captive generation offspring of wild-caught zebrafish, n>1000), we produced the F0 generation which was used to establish the respective warm-adapted, control, and cold-adapted lines. Each line consists of two replicates with ~300 fish/replicate, and we select the 33% with the highest growth rate to contribute to the next generation. Although this experiment is still ongoing, we present here the results for the F0 to F2 (n>5400) and place them in the context of key questions about the ability of animals to adapt to climate change.