Disclosed is a human serum albumin (HSA) linker and HSA linker with binding, diagnostic, and therapeutic agents conjugated thereto. Also disclosed is a conjugate in which the HSA linker is covalently bonded to amino and carboxy terminal binding moieties that are first and second single-chain Fv molecules (scFvs). Exemplified conjugates are useful, e.g., in reducing tumor cell proliferation, e.g., for therapeutic therapeutic applications. Also disclosed are methods and kits for the diagnostic and therapeutic application of an HSA linker conjugate.