Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging substitute for perfluorooctanoic acid, has been widely detected in aquatic environment and received extensive attentions of research due to its potential toxicity. However, the olfactory toxicity of HFPO-TA remains unknown yet. In the study, the effects of HFPO-TA on the olfactory epithelium (OE) and olfactory bulb (OB) were investigated in crucian carp as well as the behavioral response to olfactory stimulants. The results show that exposure to HFPO-TA inhibited the expression of genes encoding olfactory G protein-coupled receptors (GPCRs), reduced the activities of ion transporter enzymes Na