A three-dimensional porous Sb/Cu2Sb electrode is prepared by electrodeposition on a Cu foam substrate, and its electrochemical properties are investigated by a galvanostatic test for Na-ion batteries. The Sb/Cu2Sb electrode exhibits outstanding cycle stability and excellent rate capability; the charge capacity is sustained at 485.64 mA h g−1 over 120 cycles with a high coulombic efficiency of 97%, and the charge capacity retention is approximately 70% of the capacity at 0.1 C-rate, even at high 3 C-rate. The improvement in the electrochemical performance of the Sb/Cu2Sb electrode is attributed not only to the highly porous structure of the electrode but also to the improvement of bonding between substrate and active materials by the formation of Cu2Sb intermetallic. The sodiation/desodiation reactions of Sb/Cu2Sb with Na+ are proposed based on the ex-situ XRD analysis. After being fully desodiated, the electrode is restored to the crystalline Cu2Sb phase, confirming that the Cu2Sb phase reversibly reacts with Na+.