Global change is exposing freshwater ecosystems to concurrent increases in temperature and salinity. Climate change is increasing water temperatures and altering the frequency, magnitude and duration of thermal extremes, while land-use change and thermal pollution further modify freshwater temperature regimes. Concurrently, activities like agriculture and resource extraction are increasing freshwater salinization. Consequently, salinity exposure is increasingly likely under altered thermal conditions. Although various studies have assessed effects of temperature on salinity tolerance, the general effect of temperature on the salinity tolerance of freshwater organisms remains unknown. We synthesized 35 factorial temperature-salinity studies encompassing 43 freshwater species and 75 biological endpoints. The most common (53% of species) response was a decrease in LC50 as temperature increased indicating lower lethal salinity tolerance at higher temperatures. In 19% of species, lethal salinity tolerance was highest at intermediate temperatures; 7%, temperature had no effect on LC50 values. Although differences among organism groups were inconsistent, insects showed a more consistent decline in lethal salinity tolerance than other taxa. Sub-lethal EC50 responses showed no general trend with temperature, with both the direction and magnitude of responses varying among studies. Temperature sensitivity did not differ between lethal and sub-lethal salinity tolerance, but sensitivity differed among response types. Non-osmoregulatory and non-metabolic physiological endpoints were more temperature-sensitive than mortality and whole-organism (sub-lethal) performance endpoints. In summary, higher temperatures frequently reduced lethal salinity tolerance, but not universally and the response was less consistent for sub-lethal endpoints. Our results show that salinity risk assessments need to consider the combined effects of temperature and salinity. In practice, salinity tolerance should at least be measured at temperatures representative of those occurring during high-salinity exposure. More complicated approaches, e.g. incorporating temperature-salinity joint-stressor response surfaces with seasonal co-occurrence in risk models, could also be considered.