Copper slag from copper matte smelting contains iron, which forms fayalite (Fe2SiO4) as the major constituent. Because of its favorable physico-mechanical properties, copper slag has uses such as concrete aggregates, ballast, and abrasives. However, the demand for copper slag for such applications is decreasing in advanced countries such as Japan. In recent years, the depletion of high-grade iron ores and increasing demands for iron resources have resulted in an interest in the development of methods for iron recovery from low-grade metallurgical wastes. This paper gives a review of various processes such as pyrometallurgy, hydrometallurgy, and beneficiation for iron recovery and slag cleaning. Authors also proposed a new process for iron recovery from copper slag, and related simple thermodynamic calculations are provided.