For the synthesis of well-defined regular and asymmetric star-branched polymers, we have developed a new methodology using specially designed star-branched polymer anions comprised of three polymer segments in the coupling reaction with chain-end-functionalized polystyrenes with a definite number of benzyl bromide moieties (PS(BnBr)(n)). The most advantageous feature of this methodology is that three same or different polymer chains in composition can be simultaneously introduced at the core of star-branched polymer by a one-step reaction via one benzyl bromide functionality of the reaction site. By coupling these polymer anions with PS(BnBr)(2), PS(BnBr)(4), and PS(BnBr)(8), an array of 7-, 13-, and 25-armed regular star-branched polystyrenes as well as 7-armed A(2)B(2)C(2)D and 13-armed A(4)B(4)C(4)D asymmetric star-branched polymers have been successfully synthesized in ca. 100% yields. Their A, B, C, and D segments are poly(4-trimethylsilylstyrene), poly(4-methoxystyrene), poly(4-methylstyrene), and polystyrene, respectively. The resulting star-branched polymers were well-defined in branched architecture and precisely controlled in chain length. All of these results strongly demonstrate the synthetic versatility and potential of the developed methodology for the synthesis of both regular and asymmetric star-branched polymers with structural variation.