A curable silicone composition for sealing an optical semiconductor element, comprising: (A) an organopolysiloxane that has at least two silicon-bonded vinyl groups in one molecule, that has C1-10 alkyl for the other silicon-bonded organic groups therein, and that lacks a siloxane unit represented by the following formula: SiO4/2; (B) an organopolysiloxane represented by an average unit formula; (C) an organopolysiloxane that has at least three silicon-bonded hydrogen atoms in one molecule, that has C1-10 alkyl for the silicon-bonded organic groups therein, and that contains from 0.7 to 1.6 mass % of silicon-bonded hydrogen atoms; and (D) a hydrosilylation reaction catalyst, wherein a viscosity at 25° C. and a viscosity at 100° C. of this composition lacking component (D) reside in a specific relationship, can efficiently perform resin sealing by transfer molding or compression molding while exhibiting an excellent moldability and can provide a cured product that has a low surface tack.
