Teniente smelting technology produce high copper concentration slag, which are treated to reduce the quantity of copper in the slag. The slag concentration in this slag is higher than some copper mineral weight percent. At the same time, seawater is an alternative for froth flotation, given the current prevailing water crisis. The present paper study of froth flotation of copper, from smelting slag, using not desalinated seawater as fresh water. The higher copper recovery obtained was 77.27%.