Provided is a silicone composition having high curability even under low-temperature treatment conditions, and exceptional storage stability, the silicone composition being capable of imparting excellent flexibility to fibers as a fiber treatment agent, and also having exceptional washing durability; specifically, a silicone composition containing (A) 70-98 parts by mass of organopolysiloxane having a group represented by formula (1) at the end of the molecule or in a side chain (in the formula, Rx is a C1-8 divalent hydrocarbon group, a is an integer of 0-4, Ry are each independently a hydrogen atom, C1-10 monovalent hydrocarbon group, or acyl group, and at least one group shown by Ry is hydrogen) and (B) 2-30 parts by mass of blocked polyisocyanate having two or more isocyanate groups per molecule, 50% or more of these isocyanate groups being blocked by a thermally dissociable blocking agent.