Recycling of bio-waste sources for synthesis of functional electrode materials is an eco-friendly and sustainable approach to realize next-generation energy-storage systems. In this study, we present a fabrication method of Fe/C composite microfibers derived from electrospinning of hemoglobin blood protein, and subsequent calcination, and investigate its functionality as an oxygen electrode catalyst for Li-O-2 batteries. We elucidate the thermal decomposition behavior of raw hemoglobin protein and structural evolution after calcination at different temperatures. We successfully fabricated Fe/C composite microfibers with a uniform and flattened shape by electrospinning of a hemoglobin precursor and thermal treatment. Finally, we demonstrated that Li-O-2 cells in which the Fe/C composite microfiber catalyst was incorporated in the oxygen electrodes exhibited improved electrochemical performance compared to a pristine reference cell without the catalyst.