Deoxyribonucleic acid (DNA) is an attractive building block for self-assembled nanostructures, because the anionic phosphate group and the base moiety allow it to bind with a broad spectrum of organic and inorganic species through ionic and hydrogen bonding. Here we present a hierarchical structure formed by the ionic complex of DNA with an amphiphilic block copolymer comprising a cationic block. Upon the complexation the cationic block chains wrap around DNA for charge matching and the microphase separation between the hydrophobic block and the hydrophilic component yields a multilamellar structure with liquid crystalline ordering of the DNA chains condensed in the hydrophilic microdomains. Each hydrophilic lamellar domain is found to contain two DNA sublayers separated by a thin water gap, with each sublayer comprising two rows of densely packed DNA chains to lower the interfacial free energy for the present system with strong polar-nonpolar repulsion.