The alluaudite-type compound Na3.4Co1.3(MoO4)3 has been successfully synthesized by a solid-state process route. It crystallizes in the monoclinic system (C2/c), cell parameters (Å,°): a = 12.582(5) Å, b = 13.449(8) Å, c = 7.119(7) Å, β = 112.02(4)°, V = 1116.8(14) Å3, and Z = 4. Its crystal structure consists of octahedral [MO6] (M = Co, Na) and tetrahedral [MoO4] that share corners and/or edges to build the 3D framework. The sample was also characterized by X-ray powder diffraction, which confirmed crystal data, and infrared (FT-IR) and Raman spectroscopies. Its morphology was analyzed using scanning electron microscopy (SEM). The vibrational study confirms the existence of the MoO2-4 functional groups. The title compound was determined to be paramagnetic. In addition, the compound was characterized by cyclic voltammetry (CV), and its electrochemical performance and impedance were analyzed by electrochemical impedance spectroscopy (EIS). The electrochemical reaction mechanism and the limiting factors of Na3.4Co1.3(MoO4)3 as electrode material in Na-ion batteries at room temperature were also discussed. The prepared electrocatalyst showed modest hydrogen evolution reaction (HER) performance with an overpotential of 309 mV required to afford a current density of 10 mA cm−2.