Natural polymers have gained increased attention in reducing the dependence on petroleum-based materials. Chicken feather proteins are an abundant industrial by-product suitable for the fabrication of sustainable thermoplastics. However, protein-based plastics generally exhibit poor physical and thermal properties which limit their application. In this research, the fabrication of feather keratin based nano-reinforced biocomposites by the addition of graphite oxide (GO) in a reactive extrusion system were investigated. The effects of GO carbon/oxygen ratio (C/O, 2.48, 2.07, and 1.55) and concentration (0.5–2%) of the selected GO on the conformational, physical and thermal properties of thermoplastic films were investigated. Chicken feather–GO nanocomposites were successfully prepared at 150 °C in the reactive extrusion system. Tensile strength and Young modulus of chicken feather plastic films were significantly increased without affecting their elongation using low GO concentrations (0.5 to 1.5% w/w of protein). Our results suggest that higher content of hydroxyl groups and increased graphene interlayer space in GO facilitated interactions with feather keratin and plasticizers. Graphite oxide proved to be an inexpensive alternative to graphene for the reinforcement of protein based composites. Extrusion provided a cost-effective and environment-friendly method for the processing of sustainable composites.