The kinetics of chalcopyrite leaching in a ferric sulfate media for raw and mechanically activated samples has been investigated. It has been shown that the mechanism of leaching reaction is diffusion through the product layer and does not undergo any change as a result of mechanical activation in a wide range of experimental conditions. Leaching rate is strongly influenced by milling intensity and the effect of ball to powder mass ratio is stronger than milling time. Curve fitting of experimental data shows that leaching rate constant is approximately a linear function of ball to powder mass ratio, while it obeys a power function with regard to the milling time.