Abstract: Cytochrome P450 enzymes (CYPs) are encoded by P450 genes, in which cytochrome P450 1A (Cyp1a) genes mainly involve in biotransformation and metabolism of numerous xenobiotics. In this study, we cloned the Cyp1a gene from Lutjanus argentimaculatus, and investigated its tissue expression pattern. In addition, we evaluated different concentrations (10, 50 and 250 μg·L⁻¹) of BDE-3 and BDE-209 on Cyp1a gene profile and 7-ethoxyresorufin-O-deethylase (EROD) activity in liver of L. argentimaculatus. The results show that the full length of Cyp1a cDNA was 2 540 bp with 1 566 open reading frame encoding 521 amino acids. The sequence homology of L. argentimaculatus CYP1A was the highest (92.69%) with that of Lateolabrax maculatus. Phylogenetic analysis results indicate that CYP1A was closely aligned with Sander lucioperca protein. Cyp1a transcripts were most abundant in liver, followed by brain and gill, but lowest in muscle. 10 μg·L⁻¹ of BDE-3 and BDE-209 showed no effects on both Cyp1a expression and EROD activity, while high concentrations (50 and 250 μg·L⁻¹) of BDE-3 down-regulated both of them significantly in a concentration-dependent manner on 7^th-15^th day. In contrast, exposure to 50 and 250 μg·L⁻¹ of BDE-209 resulted in increasing of hepatic Cyp1a level and EROD activity. Moreover, Cyp1a genes levels and EROD activities showed a good correlation. High concentrations of BDE-3 and BDE-209 can affect Cyp1a gene expression in liver of L. argentimaculatus in different manners.