Despite the diversity of nanostructures that have been created from block copolymers over the past two decades, the challenging fabrication of polymer nanocapsules bearing regularly sized nanochannels has not been possible until now. In this study, a pseudo miktoarm copolymer mu-(PtBA)(PCEMA)(PEO)(1.14) was prepared. The copolymer consisted of 1 poly(tert-butyl acrylate) (PtBA) chain, 1 poly(2-cinnamoyloxyethyl methacrylate) (PCEMA) chain, and an average 1.14 poly(ethylene oxide) (PEO) chains. This polymer formed vesicles in a tetrahydrofuran/water solvent mixture with the soluble PEO block as the corona. At 100 units long, the PtBA chains formed cylinders that permeated the wall made of PCEMA chains at 130 units long. Photo-cross-linking the PCEMA wall and hydrolyzing the PtBA chains in the cylindrical domains yielded unprecedented capsules bearing regularly packed uniform poly(acrylic acid)-gated nanochannels. These capsules exhibited pH-responsive reagent release in aqueous media.