Polybrominated diphenyl ethers (PBDEs), which belong to the class of brominated flame-retardants, are widely used in industrial products. PBDEs have been detected in varied environmental matrices and they can induce various toxicities such as neurotoxicity, cytotoxicity, and endocrine-disrupting effects in animals. The main objective of this study was to investigate the effects of 2,2’,4,4’,5,5’-hexabromodiphenyl ether (BDE-153), 2,4-dibromophenol (2,4-DBP), and their mixtures on the endocrine system, including acetylcholinesterase (AChE) of brain, ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), and superoxide dismutase (SOD) of liver in crucian carp (Carassius auratus). Fish were exposed to BDE-153 (0.2-100 mg/kg in food), 2,4-DBP (0.2-100 mg/kg in food), and their mixture for seven days. BDE-153 alone or in combination with 2,4-DBP significantly reduced brain AChE activity and increased liver EROD activity while no significant effects were observed for 2,4-DBP alone. The simultaneously elevated GST and SOD activities were found at higher doses of BDE-153 and 2,4-DBP (alone and in combination), and exhibited obvious positive correlation (0.76<R<0.89). With regards to the induction fold of biomarker responses, 2,4-DBP has a lower toxicity than its parent compound BDE-153. However, the joint effects of BDE-153 and 2,4-DBP were not enhanced with regard to the four enzymatic activities.