In nearshore environments, exposure of marine invertebrates to low pH/low dissolved oxygen (DO) conditions fluctuate over diel timescales. It is unclear how contrasting diel variability along coastal upwelling regions can determine distinct spatial patterns in the exposure of marine populations to such extreme conditions on a daily basis, e.g. ‘upwelling center’ vs. ‘upwelling shadows’. Here, we investigate the interactive effect of diel pH and DO fluctuations on the metabolic performance of different populations of the kelp crab Taliepus dentatus during upwelling and downwelling events. We deployed DO and pH sensors in two different environmentally-contrasting coastal sites in Chile; and then the diurnal cycles of DO and pH were replicated at our laboratory under common-garden conditions. Estimates of metabolic rate and respiratory quotient (RQ) were determined along other biochemical analyses (Hemolymph pH, glucose and lactate). Oceanographic data showed clear diel fluctuations in DO/pH during downwelling, while during upwelling, DO daily cycle was maintained although with extreme hypoxia at night, and the pH diel cycle was decoupled, exposing organisms to quasi-permanent low pH conditions. When mimicking such fluctuations at the Lab, we observed that metabolism was depressed upon low pH/low DO at night. Moreover, upwelling cycle had significant impact on metabolic rates, which was depressed during upwelling. Individuals collected from the active upwelling site showed an increase in hemolymph pH and lactate content in comparison to those from the upwelling shadow, especially during low pH/low DO conditions, suggesting this boosted acid-base balance is one of the compensatory mechanisms for local adaptation.