Glass fibre reinforced polymer (GFRP) composites are increasingly adopted in construction applications due to their excellent corrosion resistance, high strength-to-weight ratio and reduced self-weight when compared with conventional materials. The density of fibre reinforced polyester composites is approximately one-fourth that of steel, while still providing comparable ultimate strength. However, the broader structural use of GFRP members is constrained by the limited availability of validated design procedures and reliable analytical models. To address this limitation, the present research examines the flexural behaviour of pultruded GFRP I-section beams through an integrated experimental and numerical investigation. Mechanical properties of the material were determined using tensile coupon tests. Full-scale GFRP beams with a clear span of 800 mm were then tested under three-point bending conditions. Finite element models were developed using ANSYS software to simulate the experimental setup. The numerical predictions displayed good correlation with the experimental results with respect to load–deflection response and stress distribution, confirming the effectiveness of finite element modelling in predicting the flexural performance of pultruded GFRP members.