This study investigates the fabrication and properties of polypropylene (PP) composites reinforced with natural sisal fiber treated with 5% sodium hydroxide (NaOH). The sisal fibers, processed with NaOH, were incorporated into PP composites at various concentrations (0–20 wt%) using the hand layup technique. The mechanical characteristics of the composites were evaluated according to ASTM standards. The composite containing 20 wt% NaOH-treated sisal fiber exhibited superior tensile strength (72.5 ± 0.5 MPa), flexural strength (103.5 ± 0.8 MPa), and hardness (43 ± 0.6 HV) compared to the un reinforced PP matrix. The study highlights the enhanced adhesive behavior and improved mechanical properties of the composite due to the NaOH treatment of the sisal fibers. The findings contribute to the development of lightweight and durable polymer composites for various engineering applications.This study investigates the fabrication and properties of polypropylene (PP) composites reinforced with natural sisal fiber treated with 5% sodium hydroxide (NaOH). The sisal fibers, processed with NaOH, were incorporated into PP composites at various concentrations (0–20 wt%) using the hand layup technique. The mechanical characteristics of the composites were evaluated according to ASTM standards. The composite containing 20 wt% NaOH-treated sisal fiber exhibited superior tensile strength (72.5 ± 0.5 MPa), flexural strength (103.5 ± 0.8 MPa), and hardness (43 ± 0.6 HV) compared to the un reinforced PP matrix. The study highlights the enhanced adhesive behavior and improved mechanical properties of the composite due to the NaOH treatment of the sisal fibers. The findings contribute to the development of lightweight and durable polymer composites for various engineering applications.