The present work was designed to develop green lightweight aggregates (LWA) using; coal fly ash, granulated blast furnace slag and small amount of cement (10–20%). Two types of lightweight concrete (LWC) were formulated using developed synthetic LWAs i.e. (i) geopolymer (GC), and (ii) Portland cement concrete (PC). Physical and mechanical properties of both LWAs and LWCs were examined for their suitability to produce LWC. Test results indicated that, density of LWA was increased and water absorption value was decreased with higher cement percentage in the developed pellet, which were complying with the ASTM requirements for LWA. Mechanical strength of produced LWAs was approximately 50% of the natural coarse aggregate. Considering LWC results, the density of LWCs was less than the threshold value (<2000 kg/m³). The compressive strength, ultrasonic pulse velocity and split tensile strength of GC were higher than PC and they were more for concretes containing LWA with higher cement percentage. Experimental strength was also compared with predicted strength from different empirical models. Overall, the properties of LWA and resulting LWC were appropriately acceptable and can offer sustainable solution to the construction industry, especially for green concrete.