Ocean acidification and warming are predicted to increase in the near future, but their effects and complex interactions on large pelagic fishes are not well known. Here, we determined the effects of elevated CO₂ and temperature at projected end-of-century levels on activity levels, boldness, and metabolic traits in larval kingfish (Seriola lalandi). Kingfish were reared from the egg stage to 25 days post-hatch in a full factorial design of ambient and elevated CO₂ (~500 µatm and ~1000 µatm) and temperature (21°C and 25°C). Activity levels were higher in fish from the elevated temperature treatment compared with fish reared under ambient temperature. However, elevated CO₂ did not affect activity, and boldness was not affected by either elevated CO₂ or temperature. Both elevated CO₂ and temperature resulted in increased resting oxygen uptake rates compared to fish from ambient conditions, but neither affected maximum oxygen uptake rates. These findings suggest that elevated temperature has a greater impact on behavioral and physiological traits of larval kingfish than elevated CO₂. However, elevated CO₂ exposure did increase resting oxygen uptake rates and interacted with temperature in complex ways. Our results can inform science and aquaculture about the future outlook of large pelagic fishes.