We report on a method for the encapsulation of DNA into polymeric nanocapsules. The encapsulation procedure involves three steps: formation of polyplexes between DNA and cationic polymeric micelles; coating of polyplexes with a cross-linked shell; dissociation of polyplexes. In the first step copolymer micelles were obtained by self-assembly of an amphiphilic polystyrene-b-poly(quaternized 2-vinylpyridine) (PS-b-PQ2VP) block copolymer in aqueous solution. Nanosized polyplexes (Dh = 190 nm and ζ = −21 mV) were formed upon the addition of DNA to the micellar solution at a phosphate/amine group ratio of 3:1. In the second step the complexes were coated with a cross-linked shell formed by seeded radical polymerization of N-isopropylacrylamide which resulted in a slight shift of ζ potential of the particles to a less negative value. The dissociation of polyplexes and removal of PS-b-PQ2VP were achieved by addition of salt and solvent exchange. Following rehydration viadialysis against water, polymeric nanocapsules with entrapped DNA were obtained. The nanocapsules were visualized by transmission electron microscopy; they exhibited smaller dimensions compared to the initial polyplexes and ζ potential very close to that of the pristine DNA.