<p>Geopolymer concrete (GPC) is an eco-friendly alternative to traditional cement concrete and has sparked widespread interest due to its potential to reduce CO₂ emissions. However, its mechanical performance, notably stress–strain behaviour for plain concrete and fiber reinforced concrete, has been a significant topic for development over the last few decades. This study examines the mechanical and stress–strain parameters of geopolymer concrete reinforced with alkali-resistant glass fibers with varying aspect ratios (444, 963) and volume fractions (0%, 0.1%, 0.2%, 0.3% and 0.4% by vol. of concrete). A series of experimental tests were conducted on geopolymer concrete viz. split tensile strength, compressive strength, flexural strength, and stress vs strain behavior of GPC. To examine the influence of fibers, binder content, aggregate proportions, and alkaline activator solution dosage were all kept constant. The obtained results indicate that the addition of alkali resistant glass fibers improved the mechanical strengths significantly, with optimal performance at 0.3% of fiber volume. The stress vs strain curves of fiber-reinforced specimens revealed enhanced ductility. An equation was proposed to generate the stress vs strain curve. The Response Surface Methodology technique was applied to investigate the effect of fiber length and fiber volume on fresh and mechanical characteristics of geopolymer concrete.</p>