In our study, Lipid peroxidation (LPO) Malondialdehyde (MDA), antioxidant enzymes such as Glutathione (GSH), Catalase (CAT) and the total protein levels in the gill tissues of zebrafish have been analysed as a response to sublethal doses of heavy metals (Cu, Zn, Cd). The study was performed on zebrafish exposed to 0.1 ppm, 0.5 ppm, 1 ppm and 5 ppm doses of copper, zinc and cadmium. The MDA, GSH, CAT and total protein levels have been measured in he-avy metal exposed zebrafish. In conclusion, the lowest sublethal doses of heavy metals have been found activate cellular antioxidative defence mechanisms.