Self-assembly of poly(2-vinylpyridine)-block-poly(ϵ-caprolactone) (P2VP-b-PCL) diblock copolymer in the presence of a selective solvent is investigated by transmission electron microscopy and atomic force microscopy. Addition of water into a P2VP-b-PCL solution in N,N-dimethylformamide at 20 °C produces elongated truncated lozenge shaped single crystals of uniform size and shape in large quantities. The single crystals are composed of PCL single-crystal layer sandwiched between two P2VP layers tethered on the top and bottom basal surfaces. The formation of the single crystals is found to depend on the temperature. These findings provide a facile approach to the preparation of uniform single crystals in large quantities.