Steel slag is an industrial waste product from steel manufacturing industries. It has potential to use in construction industry as a replacement material for crushed coarse aggregate. In this research it has been found that, shear capacity behavior of reinforced concrete (RC) beams are affected by different factors. Among the factors affecting shear behavior of RC beams, aggregate type: steel slag aggregate vs natural coarse aggregate, maximum size of aggregate and shear span to depth ratio were examined in this study. An experimental program consisting of 45 RC beams, cubes and cylinders were casted with varying percentage of replacement of natural coarse aggregate with steel slag. Test results have shown that the shear capacity of RC beams is highly dependent on percentage of replacement of coarse aggregate with steel slag aggregate, shear span to depth ratio and maximum aggregate size. Gains in shear capacity of RC beams is observed as percentage of replacement increase up to 50% replacement after that it decrease. Also shear capacity increment was observed as aggregate size increases. Beams with smaller shear span to depth ratio resulted relatively higher shear capacity as compared to beams with higher shear span to depth ratio. At 50% replacement of steel slag aggregate with coarse aggregate for the beam having a/d=2.1 and agmax=25mm the shear capacity was improved by 11.057% in relative to the control beam. Similarly, concrete cube and cylinder test results indicated that 50% steel slag replacement of coarse aggregate resulted in 23.8% and 21.99% increment in compressive strength and split tensile strength of concrete respectively