The present invention provides a grease composition for use in a constant velocity joint, which is excellent in the resistance to flaking. The grease composition comprises the following components (a) to (d):(a) a base oil; (b) a thickener; (c) an organic molybdenum compound; and (d) at least one compound selected from the group consisting of oxides of divalent typical metals having a Mohs hardness lower than that of the steel and compounds of the foregoing divalent typical metals, which can immediately be converted into the corresponding oxides of these metals having a Mohs hardness lower than that of the steel under the boundary lubrication conditions. In particular, the present invention relates to a grease composition for use in a constant velocity joint, wherein the component (d) is zinc oxide or zinc carbonate and wherein the component (c) is molybdenum dithiocarbamate.