The first use of polyether dendrons as macromolecular initiators for the controlled free radical polymerization of vinyl monomers has been demonstrated. Dendrons containing either a single benzylic TEMPO or halide functionality at their focal point have been used for the nitroxide mediated and atom transfer radical polymerizations, respectively. In both cases, hybrid dendritic-linear block copolymers with well-controlled molecular weights and low polydispersities can be obtained. The structure of the hybrid block copolymers is supported by SEC and spectral data. All the copolymers exhibit a single Tg, indicating that both blocks are miscible. Hybrid block copolymers difficult or impossible to prepare by previous techniques have been synthesized to demonstrate the versatility of this approach.