For tropical corals, the projected decreases in seawater pH due to increasing atmospheric pCO2 are predicted to reduce calcification by 8% to 40%, but little is known of the interactions with other physical conditions, or the effects on other biological processes. This study tested for the interactive effects of pH and temperature on the photosynthesis and calcification of corals using experiments in which pH was reduced (7.8), simulating year 2100 pCO2 levels, and was crossed with two temperatures (27 ºC and 29 ºC). In 14-day incubations with Pocillopora meandrina and Porites rus, calcification was depressed ≥ 50% at 27 ºC and 700 ppm CO2, compared to 27 ºC and 395 ppm CO2, but was not depressed by high pCO2 at 29 ºC; dark-adapted maximum quantum yield of PSII (Fv/Fm) was unaffected by the same treatments of temperature and pCO2. Thus, while Fv/Fm in P. meandrina and P. rus is resilient to slight increases in temperature and high pCO2, calcification shows temperature-dependent sensitivity to high pCO2, notably with high temperature apparently conferring resistance against the short-term effects of high pCO2.