Iron slag is an industrial waste by-product of steel industry. The demand for aggregate in construction industry is increasing rapidly and so is the demand for concrete. In this study the coarse aggregate (CA) were partially replaced with iron slag aggregate (ISA) at different proportions of 0 %, 10 %, 20 %, 30 % 40 % and 50 %. Compressive strength and Flexural strength on M40 grade of concrete with 0.45 water/cement ratio were investigated. In which to determine and check out the compressive strength, Flexural strength, and split tensile strength of concrete with various percentages of iron Slag Aggregate. The result has been found from the various tests which were compared with conventional concrete. Thus the use of iron slag in concrete could enhance the strength in concrete.