The increased frequency and intensity of global marine heatwaves in the past century have led to greater awareness of how these extreme events can shape aquatic ecosystems. However, few studies have considered the sub-lethal impacts of heatwaves on marine fish such as growth. We aim to assess the impact of marine heatwaves on Southeast Australian fishes by examining the effects of exposure to extreme heat on wild fish growth. Specifically, we 1) identified patterns in fish growth responses to heatwaves among species groups and life stages and 2) examined how long growth was altered by heatwaves during and after the event. We calculated a suite of physical parameters describing unique marine heatwave events, identified by satellite-derived sea surface temperatures. Then, we related heatwave attributes to individually resolved estimates of fish growth from otoliths. Overall, we found that many species experienced depressed growth during marine heatwaves, with this effect most pronounced in juvenile life stages and varied among life history traits. Our ability to anticipate the sensitivity of fish growth to heatwaves is not only important for predicting responses under future climate events but also for understanding the legacy effects of heatwaves which may alter ecosystems well into the future.