The increasing demand for durable and high-performance construction materials made high-strength concrete (HSC) a vital component in modern infrastructure. However, its inherent brittleness and low tensile strength presented challenges, particularly under tensile and bending stresses. Fiber reinforcement was widely recognized for improving the mechanical properties and durability of HSC. This study examined the influence of natural (sisal) and synthetic (steel) fibers on the mechanical properties of high-strength concrete. The research evaluated the impact of varying fiber dosages on key parameters, including compressive strength, flexural strength, tensile strength, and modulus of elasticity. Sisal fibers were added at volumetric ratios of 0.25%, 0.5%, and 0.75%, while steel fibers were incorporated at 1%, 1.25%, and 1.5%. To enhance workability and achieve high performance, 1% superplasticizer (Master Glenium51) and 8% silica fume by weight of cement were used. The results demonstrated that sisal fibers improved crack control and reduced brittleness, making concrete more resilient under tensile stresses. However, their inclusion slightly decreased density and modulus of elasticity due to increased porosity. In contrast, steel fibers significantly enhanced ductility, crack resistance, and mechanical properties, with pronounced improvements in compressive and tensile strength. These findings underscored the potential of fiber-reinforced HSC as a durable and structurally robust material, particularly for applications requiring enhanced strength, crack resistance, and long-term durability.