A grease composition includes a base oil and a thickener. The thickener contains a urea compound and a styrene-based polymer. A content of the styrene-based polymer is 2% by mass or more and 30% by mass or less as to a total amount of the urea compound and the styrene-based polymer. In the thickener, an average value of diameter of particles with a diameter of 0.2 m or more is 0.2 m or more and 1.0 m or less.