In this work, high quality iron hexacyanoferrate nanocubes (HQ-PB NCs) were synthesized through a simple hydrothermal method and then investigated as cathode electrode materials for aqueous sodium-ion batteries (SIBs), which displayed a much enhanced electrochemical performance compared with the PB nanoparticles with low quality (LQ-PB NPs). The HQ-PB NCs could be promising cathode materials for aqueous SIBs.