Self-compacting concrete is a type of concrete that does not require external or internal compaction because it becomes levelled and compacted under its own weight. Selfcompacting concrete is highly engineered concrete with much higher fluidity without segregation and bleeding. The three main requirement of self-compacting concrete are filling ability, passing ability and resistance to segregation. Also, there is initiative to re-use wastes to alleviate construction material demands and favour green construction. To this end, the present research work investigates use of steel slag fine aggregates as a partial replacement of river sand in production of self-compacting concrete. An experimental program was designed to study fresh and hardened mechanical properties of self-compacting concrete using 0%, 13%, 26%, 39%, 52% and 65% of steel slag aggregates as a partial replacement of river sand. Various workability test such as (slump flow test, Slump flow T50cm test, V-funnel test, V- funnel T5min test and L-Box test); and compressive test, split tensile test and flexural strength test were performed on 12 (150mm*150mm*750mm) self-compacted RC beams, 36 cubes (150mm*150mm*150mm)and 36 cylinders(150*300mm) specimens. Experimental results showed improved mechanical properties of SCC with various replacement of sand by steel slag. As compared to control, compresive strength increased by 22.23% at 28 days for 52% of steel slag replacement whereas flexural strength and split tensile strength enhanced by 14.59% and 13.67%, respectively. Also, test results for fresh properties indicated a slump value of 700mm; 3.5 Sec slump flows at T50cm and 1.0 L-Box blocking ratio. Overall, fresh concrete properties satisfies acceptance criteria of EFNARC and optimum value of steel slag replacement for maximized hardened concrete mechanical properties is 52%.