The enzyme activities of 7-ethoxycoumarin O-deethylase (ECOD) and glutathione S-transferase (GST), and on glutathione (GSH) content, involved in metabolism of the antibiotic Norfloxacin (NFLX), were investigated in Acipenser schrencki and Acipenser ruthenus. Sturgeons weighing 45–55 g were kept in an aquarium (0.5 m × 0.5 m × 0.9 m) for two weeks under controlled conditions (fish density 88 individuals per m3, 18°C) before the experiment. The two species of sturgeon were divided into five groups each (n = 15 in each group), with each group subdivided into three replicates of five fish per tank. A control group in which distilled water was administered orally was also tested. NFLX was forced into the stomachs of the fish at a concentration of 20, 40, 60, 80 and 100 mg kg−1 body weight, respectively. ECOD activities in liver microsomes, and GST activity and GSH content in liver microsomes and blood plasma, were measured and compared. Results indicate that ECOD activity is progressively inhibited with increasing NFLX concentrations. ECOD activity varied from 0.12 nmol mg−1 min−1 to 0.07 nmol mg−1 min−1, demonstrating an inhibition rate of 60.83% in A. schrencki and 65.14% in A. ruthenus. In both species tested, GST and GSH levels exhibited a trend of first increasing, and then decreasing with increasing NFLX levels, reaching a peak value at 40 mg per kg−1 body weight. Thus, the presented results indicate that NFLX can induce a change in the activity of some drug metabolism related enzymes such as ECOD and GST in vivo.