Controlled/living radical polymerization was developed to synthesize branched polyacrylates and polystyrene with tunable degrees of branching and low dispersities. This method is based on a polymerization induced branching process that occurs when n-butyl alpha-bromoacrylate is copolymerized under atom transfer radical polymerization conditions. This novel branching polymerization demonstrates excellent synthetic versatility, enabling the preparation of complex macromolecular architectures constructed from branched-polymer building blocks.