The aim of this study was to prepare novel bio-based maghemite (Fe₂O₃) nanocomposites as reduced graphene oxide (rGO)-doped Fe₂O₃ nanocomposites (Fe₂O₃/rGO NCs) and to investigate on their interaction with human serum albumin (HSA) as a natural polymer. Various photochemical and conformational techniques such as Fourier transform infrared spectrum, X-ray diffraction, Raman spectroscopy, scanning electron microscopes/energy-dispersive X-ray, circular dichroism, synchronous fluorescence spectroscopy, and resonance light scattering were used for characterizing the Fe₂O₃/rGO NCs and studying their interaction with HSA. The spectroscopic studies indicated that a complex formed between HSA and bio-based Fe₂O₃/rGO NCs induced structural changes on HSA. The helicity of HSA was decreased and the random coil and β-turn in the secondary structure of HSA were enhanced. In addition, the analysis of fluorescence spectra showed that Fe₂O₃/rGO NCs had a strong ability to quench the intrinsic fluorescence of HSA by static quenching mechanisms. It has been claimed that the bio-based production of nanomaterials possess no remarkable un-favored effects in biomedical fields of applications. However, the obtained results of our study demonstrate the deep influence of bio-based Fe₂O₃/rGO NCs on HSA.