<p>Growing environmental concerns have led to a focus on natural fiber-reinforced composites as sustainable alternatives to synthetic materials. Cotton and linen fibers, due to their biodegradability, offer potential for engineering applications. The mechanical performance of cotton and linen fiber-reinforced composites with epoxy and Elium® resins, focusing on tensile and flexural strength were studied. Composites were produced using the vacuum infusion method. Tensile and three-point bending tests, alongside contact angle measurements, X-ray diffraction, and scanning electron microscopy, were performed to assess thee mechanical properties, surface characteristics, and fiber-matrix adhesion. Glass fiber-reinforced epoxy composites achieved the highest tensile strength (85 MPa). Cotton fiber-reinforced epoxy and linen fiber-reinforced epoxy composites reached 60 and 50 MPa, respectively, while Elium® composites showed lower tensile strengths (cotton fiber-reinforced Elium® composite at 45 MPa, linen fiber-reinforced Elium® composite of 40 MPa). Elium® composites were more hydrophilic, especially with cotton, and displayed increased crystallinity with enhanced molecular ordering. Glass fiber-reinforced epoxy composites demonstrated superior mechanical properties; however, natural fiber-reinforced composites, particularly cotton fiber-reinforced epoxy composite, provide a viable, eco-friendly alternative for moderate-strength applications. Improving fiber-matrix interactions could enhance their suitability for broader use.</p>