Cobaltocenium-containing methacrylate homopolymer, poly(2-(methacrylolyoxy)ethyl cobaltoceniumcarboxylate hexafluorophosphate) (PMAECoPF(6)), was prepared by reversible addition fragmentation chain transfer polymerization (RAFT). Using the homopolymer as a macroinitiator, three different diblock copolymers, including a novel heterobimetallic diblock copolymer with ferrocene units as the second block, were synthesized via chain extension. Kinetic studies showed that all chain extension followed a controlled/living process under relatively lower conversion. The heterobimetallic diblock copolymer self-assembled into spherical micelles in selective solvents. The formation of aggregates depended on the location of the ferrocene block in the micelles. While the ferrocene units were susceptible to oxidation toward decomposition, the cobaltocenium moiety exhibited extraordinary stability to maintain its structure integrity.