The fresh and mechanical properties of self-compacting lightweight concrete (SCLWC) prepared by scoria and organic waste ash (OWA) were investigated, in which the OWA replaced limestone powder with different percentages. Besides, the effects of steel fiber on mechanical properties of mix designs containing 15% OWA replaced limestone powder were also investigated. To examine the fresh properties, slump flow, J-ring, and V-funnel tests were considered on fresh SCLWC, whereas compressive and splitting tensile strength were concerned for mechanical properties assessment. The results confirmed that the mix design containing 15% OWA replaced limestone powder achieved the lowest weight; however, its compressive and splitting tensile strength decreased by 28% and 20%, respectively, compared to the SCLWC made with limestone powder. Meanwhile, the inclusion of 1% steel fiber to this optimum mix design with 15% OWA replaced limestone powder increased the splitting tensile strength by 20%.