The increasing demand for eco-friendly and sustainable materials in the industrial sector has driven a shift from synthetic fossil-based materials to natural fibers and motivated the use of recycled polymer textiles. This research presents an innovative method for repurposing end-of-life textiles, such as polyester and polyamide fabrics, in the production of composite materials. The goal is to reduce textile waste and improve material longevity. The mechanical properties of composite laminates made from flax fabric (FF), flax/recycled polyamide fabric (F/RPA), and flax/recycled polyester fabric (F/RPES) were evaluated using tensile, flexural, interlaminar shear, and Charpy impact tests. Results indicate that incorporating end-of-life synthetic fibers enhances tensile strength, while flax contributes significantly to stiffness, moderated by synthetic fibers. This effect is observed in both tensile and flexural tests, with a more pronounced impact on bending stiffness. The inclusion of polyester fibers notably improved the composites, with an 11.1% increase in interlaminar shear maximum force, a 17.4% increase in interlaminar shear strength, and a 67.1% increase in un-notched impact energy compared to composites made solely with flax fiber (FF). Microscopic examination revealed a robust internal structure with a strong bond between polyester, polyamide, and flax fibers. Furthermore, the life cycle assessment showed that the F/RPES composite has a lower environmental impact than FF and F/RPA across all 18 categories analyzed, indicating a smaller environmental footprint for producing F/RPES compared to both FF and F/RPA.