Transient natural convection caused by Li+ electrodeposition at constant current along a vertical Li metal cathode immersed in a 0.5 M LiClO4-PC (propylene carbonate) electrolyte was compared with that by Cu2+ ion electrodeposition in aqueous CuSO4 solution. The concentration profile of the Li+ ions was measured in situ by holographic interferometry. The interference fringes start to shift with time at a higher current density. The concentration boundary layer thickness for Li+ ions was successfully determined. With the progress of electrodeposition, the density difference between the electrolyte at the cathode surface and the bulk electrolyte increased to induce upward natural convection of the electrolyte. The electrolyte velocity was measured by monitoring the movement of tracer particles. The measured transient behavior of the ionic mass and momentum transfer rates normalized with respect to the steady-state value was numerically analyzed. Transient natural convection along a vertical cathode due to Li metal electrodeposition can be reasonably explained by boundary layer theory, similar to the case of Cu electrodeposition in aqueous CuSO4 solution.