The impacts of warming and hypoxia on aerobic metabolism and respiratory capacity are thought to mediate the susceptibility of marine organisms to these stressors and broadly shape marine biogeographic distributions. However, how evolutionary adaptation and physiological trade-offs affect these traits under multiple stressor conditions remains unclear. Using intertidal sculpins (Actinopterygii: Cottidae), we studied how adaptation to the temperature- and oxygen-variable intertidal has shaped the temperature sensitivity of hypoxic respiratory capacity. Based on the acute temperature sensitivity of the critical oxygen tension for standard metabolic rate (Pcrit), we found that tidepool-specializing species maintain greater capacity for oxygen uptake (i.e., lower Pcrit) in warm, hypoxic water compared to subtidal species. To determine whether improved respiratory capacity in hot, hypoxic water comes with an osmoregulatory performance penalty, we measured diffusive water flux (DWF), an index of water permeability and a key component of osmoregulation, in the tidepool-specialist Oligocottus maculosus. We found that O. maculosus suppressed DWF in hypoxia but this suppression was lost during combined exposure to hypoxia and high temperature. Together these results suggest increased hypoxic respiratory capacity improves metabolic performance under combined warming and hypoxia, but physiological trade-offs between respiration and osmoregulation could reduce the marginal value of increased respiratory capacity under complex variation in temperature and oxygen conditions.