Sulfide electrolytes are very attractive materials for all-solid-state cells because of their high ionic conductivity and good elasticity. However, they are highly reactive and can be easily oxidized due to their side reactions with an oxide cathode, which acts as a major cause for the inferior electrochemical performance of the all-solid-state cells when compared with general cells using liquid electrolytes. In this study, Li2MoO4 was used as the coating material of Li[Ni0.8Co0.15Al0.05]O-2 cathode to stabilize the unstable cathode/sulfide electrolyte interface. The discharge capacity of the all-solid-state cells containing the composite electrode was increased by the introduction of Li2MoO4 coating. Moreover, the rate capability of the Li2MoO4 coated electrode was superior to that of the pristine sample. These results show that the Li2MoO4 coating is effective in suppressing the side reaction between the cathode and the sulfide electrolyte. The x-ray photoelectron spectroscopy analysis of the composite electrodes after cycling also confirmed that the Li2MoO4 coating layer reduced the formation of an unwanted reaction layer, which originates from the decomposition and oxidation of the sulfide electrolyte at the cathode/electrolyte interface.