This study explored the influence of using copper slag as an alternative sand for producing cement mortar bricks and its effect on gamma-ray attenuation property, strength, and consistency of mortar. The linear attenuation coefficients and mass attenuation coefficients were experimentally determined for mortar mixtures using the Co-60 and Cs-137 gamma-ray source, and, using the Phy-X program, attenuation parameters were theoretically calculated in 1 keV-100 GeV. Sample bricks with added copper slag were produced and tested. In the results, the added copper slag was greatly beneficial for increasing the flowability and strength of mortar, and, given all the results of attenuation parameters, the use of copper slag as aggregates was notably advantageous compared to silica sands for gamma-ray attenuation mainly due to the high Fe quantity in copper slag. The trial brick specimens using 100 wt% copper slag replacement for sand not only satisfied all requirements of cement brick in the Korean standard (KS) F 4004, but also the TCLP regulation.