Sulfate is a natural major ion commonly found in the environment. Various anthropogenic activities can lead to the discharge of sulfate in high concentrations, causing negative effects on aquatic organisms. While chronic toxicity of sulfate for brackish water species was established, acute toxicity data were scarce. In this study, we tested the acute toxicity of sulfate to seven Baltic Sea species and, together with the literature data, derived the fifth percentile hazardous concentration (HC5) through a species sensitivity distribution (SSD) with 12 species. Acute sulfate sensitivity varied across taxa, with fish and crustaceans being much more sensitive than bivalves, algae, rotifers and bacteria, which led to a bimodal SSD. The most sensitive species tested were whitefish (Coregonus lavaretus) and vendace (Coregonus albula) during fertilization, and the most tolerant were cyanobacterium Synechococcus sp. and bacterium Aliivibrio fischeri. Acute HC5 using the model-averaging approach was 2489 (1016–3990) mg/L sulfate. With a Predicted No Effect Concentration of 1011 mg/L, the upper limit of the 95% confidence interval for the estimated percentage of species affected was below 5%. This new data contributes to the development of the maximum allowable concentration for the sulfate environmental quality standard in the northern Baltic Sea.