Ocean acidification is a decrease in pH resulting from dissolution of anthropogenic CO₂ in the oceans that has physiological effects on many marine organisms. Juvenile red and blue king crabs (Paralithodes camtschaticus and P. platypus) exhibit both increased mortality and decreased growth in acidified waters. In this study, we determined how ocean acidification affects oxygen consumption, feeding rates, and growth in both species. Juvenile crab were exposed to three pH levels: ambient (pH 8.1), pH 7.8, and pH 7.5 for 3 weeks. Oxygen consumption and feeding ration were determined immediately after exposure to treatment water and after 3 weeks’ exposure. Growth was calculated as a change in wet mass. Both species exhibited initially increased oxygen consumption at pH 7.5, but not after 3 weeks. Feeding rations did not vary with pH or exposure time. Red king crabs that moulted grew more in ambient water than in pH 7.5. The initial increase in oxygen consumption at pH 7.5 suggests the crab increased metabolism and expended more energy in osmo-/iono-regulation. Without an increase in feeding ration, it is likely the crab reduced energy expenditure in other areas, explaining the reduced growth and increased mortality observed in this and other studies.