We present a method to induce cell directional behavior using slanted nanocilia arrays. NIH-3T3 fibroblasts demonstrated bidirectional polarization in a rectangular arrangement on vertical nanocilia arrays and exhibited a transition from a bidirectional to a unidirectional polarization pattern when the angle of the nanocilia was decreased from 90 degrees to 30 degrees. The slanted nanocilia guided and facilitated spreading by allowing the cells to contact the sidewalls of the nanocilia, and the directional migration of the cells opposed the direction of the slant due to the anisotropic bending stiffness of the slanted nanocilia. Although the cells recognized the underlying anisotropic geometry when the nanocilia were coated with fibronectin, collagen type I, and Matrigel, the cells lost their directionality when the nanocilia were coated with poly-D-lysine and poly-L-lysine. Furthermore, although the cells recognized geometrical anisotropy on fibronectin coatings, pharmacological perturbation of PI3K-Rac signaling hindered the directional elongation of the cells on both the slanted and vertical nanocilia. Furthermore, myosin light chain II was required for the cells to obtain polarized morphologies. These results indicated that the slanted nanocilia array provided anisotropic contact guidance cues to the interacting cells. The polarization of cells was controlled through two steps: the recognition of underlying geometrical anisotropy and the subsequent directional spreading according to the guidance cues.