A curable silicone composition is disclosed. The curable silicone composition comprises: (A) a linear organopolysiloxane having at least two silicon atom-bonded alkenyl groups per molecule, wherein at least 5 mole % of all silicon atom-bonded organic groups are aryl groups; (B) an organopolysiloxane containing siloxane units represented by the general formula R13SiO1/2 where each R1 represents an independently selected monovalent hydrocarbon group, and siloxane units represented by the general formula SiO4/2, wherein the amount of alkenyl groups is at least 6% by weight; (C) an organopolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule; and (D) a hydrosilylation reaction catalyst. The curable silicone composition forms a cured product with little weight reduction, little change in hardness, and little crack generation after thermal aging.