Productive marine coastal ecosystems such as coral reefs, seagrass meadows, kelp forests and mangroves are characterised by circadian fluctuations of oxygen controlled by temperature and the cycle of photosynthesis and respiration of the primary producers. Marine species living in such productive coastal habitats have therefore evolved in highly dynamic diel and seasonally fluctuating environments. Consequently, studies strictly based on rigorous laboratory conditions may not capture, or test, the real effect of environmental fluctuations on the thermal tolerance of marine species, which is directly linked with environmental oxygen availability. In this study we selected three areas, across a large latitudinal scale, with different levels of temperature and oxygen fluctuations and predictability. By incorporating lab experiments with ecologically relevant oxygen levels recorded from the field, we hypothesized that the degree of the diel environmental fluctuations in the coastal areas can explain the thermal response of marine species. To test this hypothesis, we measured the thermal tolerance of 17 marine ectotherm animal species from the three different locations, from tropical to warm and cold temperate environment. Our results showed that higher predictability of oxygen and temperature fluctuation increases the magnitude of species’ thermal tolerance compared to those in less predictable environments. We advocate that ecologically relevant environmental oxygen fluctuation needs to be considered when measuring and forecasting the response of marine animals to global warming and it provides a new background to assess aquatic communities’ thermal tolerance.