Manganese hexacyanoferrate was prepared via the hydrothermal method and its cubic structure was established. Manganese hexacyanoferrate powder was examined in the composition of a cathode material for sodium-ion batteries with an electronically conductive carbon black additive and a polyvinylidene fluoride binder polymer. The electrochemical properties of manganese hexacyanoferrate-based electrodes in a propylene carbonate solution of sodium perchlorate were investigated using cyclic voltammetry and charge-discharge curves. The specific capacities of the cathode material and their dependence on the current density were observed. The stability of the capacitive characteristics of the material was considered during long-term charge-discharge cycling.