This study deals with evaluation of steel slag utilization as filler material in hot mix asphalt. Steel Slag is generated as waste material or by-product from steel industries. According to large number of steel making factories all around the world, in recent years many researches have been done minimize environmental impacts of this waste by using it again in production of different materials like hot mix asphalt Mixtures (HMA). In this study, Steel slag has been obtained from Ethiopian iron and steel factory, were applied to produce an environmental friendly HMA. Marshall Specimens were prepared for different bitumen content (3.5%−5.5% at 0.5% increments) by using 2.5% Stone dust filler (SDF) in control mix as well as varying percentage of Steel Slag (SS) ranging from 2.5% to 10% as alternative filler in modified mixes. In total, 90 samples were prepared, 75 of which have been used to determine the OBC for each slag content, and the rest have been used to find out the Marshal properties at OBC for different percentages of slag filler in the asphalt mixture. Laboratory testing has revealed an enhancement in the mechanical performance of asphalt concrete mixtures when Steel Slag was used. Marshall Stability and unit weight increased with the increase of Steel Slag content. The voids of total mix (% Va) and voids of mineral aggregate (% VMA) values decreased as the Steel Slag content increased. The optimum asphalt content decrease with the change in Slag content. Using Steel Slag content more than 7.5% caused an increase of Optimum bitumen Content and flow value of the mixture. HMA mixtures containing 7.5% Steel slag have greater rutting resistance than other tested mixtures. It can be stated that the successful utilization of waste materials in pavement construction can provide a new and more cost effective approach, and decrease the threats of industrial solid wastes to environment.