Nonaqueous redox flow batteries (NARFBs) have the potential as high-energy-density electrochemical storage systems due to their wider electrochemical windows compared with their aqueous counterpart. Before possible commercial application, three major performance metrics (energy density, power density, and cycling stability) of NARFBs need to be improved. With molecular diversity and scalability, redox-active organic materials (ROMs) are considered as promising redox-active materials for establishing sustainable NARFBs. Reasonable molecular engineering ROMs can obtain desired physicochemical properties, leading to the improvement of battery performance metrics. This mini review comprehensively summarizes the NARFB improvement through molecular engineering ROMs over the recent years, aiming to provide a guideline for the future battery design.