This study investigates the flexural behavior of fibre-reinforced polymer (FRP) bars after being subjected to different levels of elevated temperatures (100, 200, and 300°C). Three types of glass FRP bars (ribbed, sand-coated, and helically wrapped) and one type of carbon FRP bars (sand-coated) were used in this study. Two testing scenarios were applied: (a) testing specimens immediately after heating and (b) allowing specimens to cool down to room temperature before testing. The results showed that as the temperature increased, the flexural strength and modulus of the tested FRP bars decreased. At temperatures higher than the glass transition temperature (Tg), significant flexural strength and modulus losses were recorded. Smaller diameter bars showed better residual flexural strength and modulus than larger diameter bars. The bars tested immediately after heating showed significant strength and modulus losses compared to bars tested after cooling. Different types of GFRP bars exhibited comparable results. However, helically wrapped bars showed the highest flexural strength losses (37% and 60%), while sand-coated bars showed the lowest losses (29% and 39%) after exposure to 200 and 300°C, respectively. The carbon FRP bars exhibited residual flexural strengths comparable to those of the GFRP bars; however, they showed lower residual flexural modulus after being subjected to 200 and 300°C.