The electrochemical performance of sodium Prussian Blue Na1-xFeIII 1+(x/3)[FeII(CN)6]·yH2O in aqueous electrolyte is here reported. Remarkable cycling stability and coulombic efficiency close to 100% have been achieved by suppressing the process at high voltage since results in Na-PB peptization and electrode disintegration. Under these conditions, this material is able to deliver 65mAhg−1 of capacity, which is slightly higher than the capacity obtained in organic electrolyte despite the voltage window used in aqueous electrolyte is narrower. This is possible thanks to the significant reduction of overpotential in aqueous medium which is here discussed and compared with previous results obtained with NaFePO4 in aqueous electrolyte.