The dispersion polymerization of styrene using a poly(4-vinylpyridine) (P4VP) macromolecular RAFT (macro-RAFT) agent as both a macro-initiator and a colloidal stabilizer under UV radiation was investigated for the first time. The P4VP macro-RAFT agent ($M_{n,GPC}$=49,000 g/mol, PDI=1.14) was prepared by the RAFT polymerization of 4-vinylpyridine using 2-cyanoprop-2-yl dithiobenzoate as a chain transfer agent. The resulting polystyrene (PSt) particles had hairy P4VP chains, which could successfully immobilize very small Au nanoparticles on the surface of the PSt particles. It was found that hairy polymeric particles could be produced by photo-initiated dispersion polymerizations of vinyl monomers using macro-RAFT agents that are susceptible to UV radiation as both macro-initiators and colloidal stabilizers.