Concrete loses a significant portion of its strength when exposed to elevated temperatures, making the enhancement of its thermal performance an important research objective. This study aims to evaluate the effect of carbon fibers on improving the fire resistance of concrete. Various fiber contents (0.5%–2% by cement weight) were used to investigate their influence on workability, compressive strength at ambient and elevated temperatures (250°C, 450°C, and 800°C), water absorption, and indirect tensile strength at 28 days. The results indicated that the addition of carbon fibers reduced workability, while the mix containing 1% carbon fibers showed relatively stable compressive strength at 250°C and a noticeable improvement at 450°C. Overall, carbon fibers exhibited a dual effect, presenting challenges in fresh properties while enhancing the mechanical and thermal performance of concrete. ........................ Keywords:................. Concrete, Carbon fibers, Workability, Compressive strength, Indirect tensile strength, Fire resistance.