This paper presents a study about the effects of freeze-thaw cycles (FTC) on the durability of 8 mm thick pultruded glass fibre-reinforced polymer (GFRP) composite laminates manufactured with unsaturated polyester (UP) and vinyl ester (VE) resins. After 100, 200, and 300 FTC, the retention of tensile, compressive, flexural, in-plane (IP), and interlaminar shear (ILSS) strengths in the longitudinal (pultrusion) direction were assessed under wet and dry conditions. The GFRP_UP exhibited the lowest retention of compressive strength, down to 73% under wet conditions after 100 FTC, with partial recovery to 85% after 300 FTC, while IP shear strength retention increased up to 111% under dry conditions after 100 FTC, followed by a reduction to 88% under wet conditions after 300 FTC. The GFRP_VE showed a better overall performance, with a tensile strength retention of 91% under wet conditions after 300 FTC. However, ILSS retention for GFRP_VE showed notable reductions, down to 77% under dry conditions. For both composites, the flexural strength exhibited small variations, suggesting that the flexural response was dominated by the fibre reinforcement and that fibre-matrix adhesion remained effective throughout the exposure. The results highlight that while both composites exhibited satisfactory performance under FTC, the GFRP_VE generally showed better durability (maintaining higher retention of tensile, compressive, and in-plane shear strengths under wet conditions), although the GFRP_UP showed slightly higher retention of ILSS when exposed to moisture.