Coral reefs are being increasingly exposed to multiple environmental stressors including ocean warming and acidification. From previous single and multi-stressor studies we know that in general warming negatively effects a broader range of traits (e.g. physiology, growth, behaviour) than elevated CO2, which largely influences behavioural traits. When exposed to both environmental stressors simultaneously within a single generation, a negative relationship was found between a performance trait associated with elevated temperature, and another predominantly associated with CO2 for the coral reef damselfish (Acanthochromis polyacanthus). However, with projected climate change most coral reefs will experience warming well before acidification and this earlier experience of warming may allow thermal plasticity to occur. In this study, two generations of A. polyacanthus were exposed to either present-day control (+0°C) or elevated temperature (+1.5°C) at various life stages, allowing for both development and transgenerational plasticity to occur. Using the third generation, this study investigated how this thermal plasticity in previous generations influences the sensitivity of the current generation to the same elevated temperature (+1.5°C) and CO2 (825 ppm) both independently and combined. After developing in these environmental conditions for 16 weeks, aerobic physiology (resting metabolic rate, maximum metabolic rate, and net aerobic scope), behaviour (activity and boldness), and growth (length, weight, and condition) of juveniles was measured and the relationship between these performance traits explored.