Disclosed is a binder composition for secondary batteries, wherein conjugated diene latex particles (A) having an average particle diameter of 50 nm or more and 200 nm or less and acrylic copolymer latex particles (B) having an average particle diameter of 300 nm or more and 700 nm or less are present as an independent phase, and the acrylic copolymer latex particles (B) are included in an amount of 1% to 30% by weight based on a mass of a solid. When the binder composition according to the present invention is applied to an electrode mixture and lithium secondary battery, superior binding force may be maintained between electrode materials and between an electrode material and a current collector, which suffer volume change during charge/discharge, and a secondary battery having superior initial capacity and efficiency may be provided. In addition, thickness increase and gas generation are decreased at high temperature and thus swelling is decreased, whereby a battery having enhanced safety may be provided.