Miniemulsion polymerization with an amphiphilic poly(acrylic acid)-block-polystyrene reversible addition-fragmentation chain transfer agent as a surfactant and polymerization mediator is used to synthesize highly uniform nanocapsules. The nanocapsules with uniform structures, which include particle size, shell thickness, and shape symmetry, could be achieved by the post-addition of a small amount of sodium dodecyl sulfate. Although the solid particles seem unavoidable, the 'pure' uniform core-shell structures are easily collected by centrifugation.