Nano-sized cobalt-substituted magnetite has been synthesized and used as a heterogeneous Fenton catalyst for the removal of anticancer drug Flutamide (FLU) from a solution with a concentration of 150 mu M. By using response surface methodology at the optimal conditions of Fenton oxidation (FO) process, 67.7% FLU removal was obtained. In order to increase the removal efficiency of the drug, ozonation was applied in combination with FO process. Maximum FLU removal (93.0%) was obtained using 0.6 g O3 l(-1)h(-1) and 163 mg L-1 of the catalyst. The results indicate that the proposed method is efficient for the degradation of cytotoxic drugs.