<p>This study presents a comprehensive experimental work on microstructural characteristics, mechanical, and transport properties of glass fiber-reinforced metakaolin geopolymer composite. The basic material aspects, including fluidity, setting time, porosity, flexural, uniaxial tensile, and compressive strength, are first examined on samples with different fiber volume fractions of 0%, 0.2%, 0.5%, and 0.8%. An optimal glass fiber dosage of 0.5% is selected. Then the complete mechanical behavior of optimized composite samples is investigated through triaxial compression tests with different confining pressures, in particular stress–strain relations, failure strength, and modes. Gas permeability is further measured and analyzed in relation with porosity. Based on the experimental data obtained, some new findings are issued. The studied fiber-reinforced metakaolin-based geopolymers show a mesoporous structure. The mechanical behavior is significantly influenced by confining pressure. The Mohr–Coulomb criterion can be adopted to describe the failure envelop of materials in the stress range considered here. The permeability is also affected by confining pressure in relation of porosity evolution.</p>