Epitaxial crystallization onto a directionally crystallizable organic solvent, 1,3,5-trichlorobenzene, was applied to polymer blends containing regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) and either polystyrene (PS) or regiorandom poly(3-dodecylthiophene-2,5-diyl) (P3DDT). Well-ordered lamellae-in lamella and dots-in-lamella structures were observed for P3HT/PS and P3HT/P3DDT, respectively. P3HT/PS gave more-discernible lamellar nanopatterns than did P3HT/P3DDT, owing to miscibility differences. Grazing-incidence wide-angle X-ray diffraction analysis, and polarized UV-visible absorption spectroscopy revealed that the P3HT crystalline lamellae were oriented edge-on in the thin films. Polymer blend nanostructures were also obtained when a third component, phenyl-C-61-butyric acid methyl ester, was present, thus demonstrating the potential of this strategy for engineering the nanostructure of the active layers in P3HT-based electronic devices.