The purpose of our experiment was to evaluate the effect of enrofloxacin on biotransformation, oxidative stress and mRNA expression of related genes in fish as a non-target organisms. Zebrafish (Danio rerio) juveniles were treated with enrofloxacin at concentrations of 5, 10 and 500 μg/L for 14 days. A three-day-long test caused changes of catalytic activity of glutathione peroxidase and glutathione-S-transferase. Moreover, lipid peroxidation was observed at the highest concentration. No significant changes either in catalytic activity of antioxidant enzymes or elevated lipid peroxidation were observed from sampling day 7 on. mRNA expression of genes encoding antioxidant enzymes was also not affected by enrofloxacin after a 14-day exposure. This suggests the ability of D. rerio juveniles to adapt to enrofloxacin in a short time period. Moreover, enrofloxacin was not shown to affect collagen, cathepsin K, optic atrophy 1 and pyruvate kinase L/R mRNA expression in this study.