A grease composition for a constant-velocity joint includes a mineral oil, a thickener, a molybdenum dithiocarbamate, a potassium borate hydrate, and a zinc dialkyldithiophosphate, wherein a content of the molybdenum dithiocarbamate is 1.2% by mass or more and 8% by mass or less, a content of the zinc dialkyldithiophosphate is 0.3% by mass or more and 2.0% by mass or less, and a content of the potassium borate hydrate is 0.28% by mass or more and 1.9% by mass or less, and wherein a mass ratio of the content of the molybdenum dithiocarbamate to the content of the potassium borate hydrate (molybdenum dithiocarbamate/potassium borate hydrate) is 2 or more and 13 or less, and a mass ratio of the content of the zinc dialkyldithiophosphate to the content of the potassium borate hydrate (zinc dialkyldithiophosphate/potassium borate hydrate) is 0.5 or more and 3.6 or less.