A new strategy for control of the in-plane orientation of azimuthal pentacene molecules using imprinted nanometer-scale periodic groove patterns for organic thin-film transistors (OTFT) as an alignment layer was introduced. Pentacene channels were deposited on the patterned alignment layer for the fabrication of the OTFT, and gold was thermally evaporated through a shadow mask to form the source/drain electrodes. The results show that the anisotropic mass transport along the nanometer-scale relief of the substrate is responsible for the enhanced crystal growth in the direction parallel to the grooves. Two absorption peaks at 581 and 667 nm and two shoulders at 542 and 629 nm are observed in the absorption spectra of pentacene. The results also indicate that the nanometer-scale patterns allow most of the pentacene molecules to nucleate along the grooves as the size of the monolayer island of pentacene is comparable to that of the space between the grooves.