This study explores the viability of chicken feather-reinforced thermoplastic polyurethane (TPU) composites as environmentally sustainable materials. Chicken feathers, an abundant keratin-rich biowaste generated by the poultry industry, were processed into both powder and fiber forms and subsequently subjected to chemical modification using (3-aminopropyl) triethoxysilane to enhance interfacial compatibility with the TPU matrix. Four composite formulations were produced via melt compounding, incorporating TPU-to-feather weight ratios of 90:10 and 85:15 for each morphological variant. Standardized test specimens were fabricated and evaluated through tensile, compressive, hardness, and density analyses. Among the formulations, the composite containing 85% TPU and 15% feather fiber exhibited the most favorable mechanical properties. The improved interfacial adhesion was attributed to the dual functional role of the silane coupling agent, which facilitated both covalent and hydrogen bonding at the filler–matrix interface. The findings underscore the potential of chemically treated feather waste as an effective and economical reinforcement for polymeric materials, advancing the development of high-performance, sustainable composites.