Chalcopyrite leaching rate in atmospheric pressure and in sulfate media with ferric ion is low because of passive layer formation around chalcopyrite particles. In this investigation pyrite is used as a catalyst of chalcopyrite leaching. Because of galvanic interaction between chalcopyrite and pyrite, the chalcopyrite leaching rate is increased. Effects of parameters such as stirring speed, pyrite to chalcopyrite ratio, solution potential, temperature, and initial acid concentration were investigated. Results showed that maximum copper recovery (more than 95%) is obtained in less than 24 h, stirring speed of 1150 rpm, pyrite to chalcopyrite ratio 4, solution potential 410 mV, temperature 85 degrees C, and initial sulfuric acid concentration 45 g/L. Also, kinetic investigation showed that chalcopyrite dissolution in the presence of pyrite followed the shrinking core model and the reaction was controlled by the surface reaction. Activation energy (E-a) was calculated at 77.79 kJ/mol. Surface studies showed that in the absence of pyrite, the surface of chalcopyrite particles was covered by passive layer.