Freshwater salinization is increasing due to climate change, agriculture, urbanization, mining, and other anthropogenic activities, threatening freshwater animals and their ecosystems. Still, studies of taxon-specific responses and comparisons across major aquatic groups are rare. Understanding taxon-specific salt responses will allow us to better understand taxon sensitivities and therefore help prioritize conservation efforts across groups. We conducted a comprehensive review of freshwater animal responses, characterizing 5924 responses across 585 articles of freshwater mollusks, crustaceans, zooplankton, non-arthropod invertebrates, insects, fishes, and amphibians. Common focal ions across all studies and groups included Na+and Cl- based ions, as opposed to more toxic ions such as K+, HCO3-, Mg2+ and ion mixtures that commonly result from resource extraction, irrigation, and urban infrastructure. As expected, negative responses to salinization predominated within all taxonomic groups across all laboratory and field studies: 78% for non-arthropod invertebrates, 68% for zooplankton, 62% for amphibians, 62% for insects, 56% for mollusks, 56% for freshwater crustaceans, and 51% for fishes. Insects were the most well-studied of these taxa, with 26% of reviewed articles focusing on insect-salt responses. Effect sizes will be calculated for all taxa at the individual- and population-level and compared within the context of different ions and primary threats. Insect-specific responses to salinization have been reported, but other taxon-specific salt-response predictions are less known. We predict that taxa with shorter life spans, external respiratory structures, and multiple life stages are traits that confer greater sensitivity to rising salt ion concentrations in freshwater systems. Knowledge of taxon-specific responses could help identify the most immediate conservation needs across taxonomic groups.