Sodium Prussian blue (SPB) with a cubic structure was successfully synthesized by a simple precipitation method in a hot acidic medium. Scanning electron microscopy images showed that the as-prepared SPB consisted of many microcubic structures with different morphologies and sizes because of the tailoring of its surface morphology by etching. The Fourier-transform infrared spectroscopy and energy-dispersive X-ray spectroscopy results indicated the existence of interstitial water and the replacement of Na+ ions by H+ ions in the SPB material. In addition, when used as a sodium-ion battery (SIB) cathode, the as-prepared SPB showed significantly different electrochemical behaviors in two different alkyl carbonate electrolytes (ethylene carbonate and propylene carbonate with 2% fluoroethylene carbonate electrolyte (EC-PC-2% FEC) and PC-2% FEC electrolyte). The results showed that in the PC-2% FEC electrolyte, the as-prepared SPB showed excellent rate capability and cycle stability, and hence was found to be a promising SIB cathode material.