The environmental impact of Portland cement has motivated the development of fly ash-based geopolymer concrete (GPC), but its inherent brittleness and low tensile strength limit its structural applications. Research has investigated the effects of multi-walled carbon nanotubes (MWCNTs) or polypropylene fibers(PP) independently in geopolymer systems, and there is limited research on the effects of combined reinforcement of MWCNTs and PP fibers in a fly ash-based geopolymer matrix, especially with systematic evaluation at different curing ages and reinforcement ratios. This study investigates a multi-scale reinforcement approach using (PP) fibers and (MWCNTs) to enhance the mechanical and microstructural performance of fly ash-based GPC. Thirteen concrete mixtures with class F fly ash, MWCNT content from 0 to 0.6 wt% and PP fibers from 0 to 0.2 vol% were prepared at 7, 14 and 28 days of curing. Mechanical tests (compressive, tensile and flexural strengths) were performed along with microstructural analyses (XRD, XRF and SEM-EDX). The optimized hybrid reinforcement (0.1% PP fibers and 0.6% multi-walled carbon nanotubes) increased the compressive strength by 63% and the optimized hybrid reinforcement (0.2% PP fibers and 0.6% multi-walled carbon nanotubes) increased the tensile strength by 120% and flexural strength by 61% compared to plain GPC. Meanwhile, scanning electron microscopy (SEM-EDX) confirmed the increase in matrix density, fiber-matrix bonding, and the formation of silicate aluminate (Si-O-Al) gel. These findings indicate that the PP-MWCNT hybrid reinforcement significantly enhances the structural performance of GPC. These results provide a promising direction for the development of high-performance and carbon-reducing geopolymer-based composites for sustainable construction.