The utilization of natural fibers in engineering applications necessitates a precise evaluation of their dimensional and mechanical properties. Researchers are exploring these fibers as potential construction materials for cement, mortar, and concrete. Sisal fibers may be used as a reinforcing ingredient in concrete because of their affordability, high strength-to-weight ratio, and recyclability. Sisal fiber-reinforced concrete composites offer advantages over conventional materials due to their enhanced mechanical strength, stiffness, and fatigue properties, which allow for greater flexibility in structural design. Additionally, sisal composites are more environmentally friendly and biodegradable than traditional materials, supporting sustainable building practices. This research explores Na2CO3 treatment on sisal fiber's resistance to deterioration and the longevity of sisal fiber-reinforced concrete are investigated. Sisal fiber was added at varying percentages (0.5% to 1.5% by cement volume) with a length-to-diameter ratio of 100 in M30 grade concrete, following IS 10262:2009 standards. The work included Fiber tensile strength testing, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and durability tests against chloride and sulphate attack. Results showed that 2% Na2CO3 treatment increased Fiber tensile strength from 254 MPa (untreated) to 332 MPa, improving Fiber-matrix bonding. SEM and EDX confirmed denser interfacial transition zones and higher Ca-Si hydration products in treated composites. Durability tests revealed that sisal Fiber reinforced concrete (SiFRC) exhibited lower strength loss under chloride and sulphate exposure compared to conventional concrete, with 1.25% Fiber addition showing optimal performance. These findings demonstrate that eco-friendly sisal Fiber, when chemically treated, can enhance strength and durability of concrete, supporting its use as a sustainable alternative to synthetic Fibers.