Laboratorys studies were conducted to determine the acute toxicity of three fire retardants (Fire‐Trol GTS‐R, Fire‐Trol LCG‐R, and Phos‐Chek D75‐F), and two fire‐suppressant foams (Phos‐Chek WD‐881 and Ansul Silv‐Ex) to early life stages of chinook salmon, Oncorhynchus tshawytscha, in hard and soft water. Regardless of water type, swim‐up fry and juveniles (60 and 90 d posthatch) exhibited similar sensitivities to each chemical and these life stages were more sensitive than eyed eggs. Foam suppressants were more toxic to each life stage than the fire retardants in both water types. The descending rank order of toxicity for these chemicals tested with swim‐up fry and juveniles (range of 96‐h median lethal concentrations [LC50s]) was Phos‐Chek WD‐881 (7–13 mg/L) > Ansul Silv‐Ex (11–22 mg/L) > Phos‐Chek D75‐F (218–305 mg/L) > Fire‐Trol GTS‐R (218–412 mg/L) > Fire‐Trol LCG‐R (685–1,195 mg/L). Water type had a minor effect on the toxicity of these chemicals. Comparison of acute toxicity values with recommended application concentrations indicates that accidental inputs of these chemicals into stream environments would require substantial dilution (237‐ to 1,429‐fold) to reach concentrations equivalent to their 96‐h LC50s.