It is highly economical to extract keratin from the waste chicken feathers due to their high keratin content, plentiful availability, and sustainable resources. Various methods of keratin extraction have been reported in the last few decades. In addition, sodium sulfide (Na2S) treatment has received more attention due to its simplicity and ability to produce on an industrial scale. Although several studies have been conducted on improving keratin extraction yield through Na2S treatment, there need to be more systematic studies to evaluate and optimize the effect of different extraction parameters and their interactions to maximize extraction efficiency. In this research, the response surface method (RSM) established on the central composite practical design (CCPD) was employed satisfactorily to understand the influence of experimental parameters and their interactions to determine the optimal conditions for keratin extraction. Na2S concentration, extraction time, and extraction temperature were chosen as the most critical parameters for investigation. Experimentally, the extraction yield of 94±0.5% was obtained under the RSM-optimized conditions (i.e. 80 °C, 6.3 hr., and 32.0 g l-1 Na2S concentration), which is in close agreement with the model-predicted value (95%). The optimized keratin extraction yield in this study is relatively high. Physicochemical properties of the extracted powder were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results revealed that the extracted material contains both β-keratins and α-keratins, which have great potential for advanced healthcare and medical applications.