The co-deposition of Al and Zn on AZ91D magnesium alloy from a Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EMIC, with a molar ratio of 60:40) ionic liquid containing 1 wt% ZnCl2 at room temperature was studied. The effect of potential on the deposition rate, the microstructure and the chemical composition of the deposit was explored. The experimental results show that the simultaneous deposition of Al and Zn on Mg alloy can be achieved under properly controlled potential conditions. The deposition rate increased while the amount of Zn existing in the coating decreased with increasing negative deposition potential. In the ionic liquid studied, a uniform chemical composition of the coating was obtained when the deposition was performed at -0.2 V (vs. Al).