A binder composition for a secondary battery which includes a copolymer binder including at least one unit selected from (A) a unit derived from a vinyl-based monomer, (B) a unit derived from a conjugated diene-based monomer or a conjugated diene-based polymer, (C) a unit derived from a (meth)acrylic acid ester-based monomer, and (D) a unit derived from a water-soluble polymer, wherein the copolymer binder has a wet modulus of 0.02 MPa or more, and a negative electrode for a lithium secondary battery and a lithium secondary battery which include the same.