Spin‐crossover (SCO) nanorod arrays have been fabricated by a very simple construction method with cation‐exchange polymer resin beads as templates. The nucleation and growth mechanism of the nanorod arrays was studied by SEM. The spin‐crossover properties of nanorod arrays with different growth times were characterized by differential scanning calorimetry (DSC), Mössbauer spectroscopy, and magnetic susceptibility measurements. The transition temperatures of the obtained nanorod arrays increase as the immersion time of the nanorods increases. The hysteresis loop widths of these nanorod arrays are larger than that reported for [Fe(Htrz)2(trz)][BF4] (Htrz = 1,2,4‐triazole) as bulk powder and nanoparticles. This offers a new route for the fabrication of ordered SCO nanorod arrays by a self‐assembly method.