A grease composition comprising a grease containing, in a base oil thereof, from 2 to 40% by weight, based on the total composition, of tricalcium phosphate [Ca.sub.3 (PO.sub.4).sub.2 ], the grease further containing (A) from 0.5 to 10% by weight, based on the total composition, of a molybdenum dialkyldithiocarbamate sulfide and (B) from 0.1 to 5% by weight, based on the total composition, of at least one of a zinc dialkyldithiophosphate and triphenyl phosphorothionate. The grease composition is excellent in mechanical stability, heat resistance, extreme pressure properties, and wear resistance.