<p>This research investigates the impact of employing metakaolin (MK) on the mechanical and fresh properties of hardened geopolymer (GP) concrete reinforced with polypropylene fibers. For this reason, GP composite is made with ground-granulated blast-furnace slag, sodium hydroxide, sodium silicate, and microsilica. The concrete mix is made using standard procedures, and samples are molded. The weight percentage of MK ranges from 0% to 20% of ground-granulated blast-furnace slag, whereas the weight percentage of polypropylene fibers varies from 0% to 0.8% of the binder. The findings show that 10% of MK is needed on average to achieve the maximal compressive strength of GP concrete. The GP concrete strength increases by approximately 15% as a result of these values. With 0.4% of the slag weight in polypropylene fibers, the maximum compressive strength was attained. Concrete’s compressive strength increases by roughly 11% on average when this quantity of fibers is used. This is also true for the splitting test of flexural and tensile strength. According to the water absorption measured on examined concrete samples, hardened concrete absorbs less water when MK is increased. The amount of water absorbed increases with polypropylene fiber consumption, and the least amount of water absorbed occurs when polypropylene fibers are not used. Water absorption is increased by approximately 9% on average when fiber content rises from 0 to 0.8% of slag weight.</p>