The use of a Chilean copper smelter slag in the manufacture of cement mortars was studied. Copper slag was characterized from the chemical, mineralogical and size distribution point of view. In addition, different Chilean standards were used to determine some important parameters of the waste and to perform compression and flexural assays of the cement mortars. The results obtained showed that the mortars manufactured with copper slag present a higher resistance to compression and flexural than those manufactured with river sand. It is concluded that this metallurgical residue can be used in civil construction.