This study investigates the potential of using steel slag blended grouts for 3D concrete printing applications. Steel slag, a by-product of the steel-making industry, is considered chemically less reactive compared to other supplementary cementitious materials. However, finely ground steel slag can influence the fresh-state properties of Portland cement mortars used for 3D printing. The effect of steel slag addition on the flow and static yield strength of mortars made with different Portland cement to steel slag ratios was evaluated. Effectiveness of commercial chemical admixtures enhancing the extrusion properties of Portland cement–steel slag blended mortar at the mixing stage, and further for the on-set of mortar after extrusion from the printing nozzle was determined for one selected mix design. Results indicate that adding steel slag reduces the static yield strength of the mix design required for structure build-up. Nevertheless, the accelerating admixture at the printing nozzle of the 3D printer (bi-component, 2K) helps gain the static yield strength required for buildability. Findings reveal that accelerator admixture has no impact on the mechanical performance of mortar containing 50 wt.% steel slag of the solids. However, superplasticizers can influence the flow retention property like the open time of the mortar. On the other hand, a higher proportion of steel slag has proven beneficial in inducing better extrusion properties. Printing of laboratory-scale hollow cylindrical geometry with same selected mix design has shown better buildability without any yielding of printed layer or buckling. In general, this study gives a perspective on using Portland cement–steel slag blended mortar for 3D printing applications.