A cobalt nanoplate array (Co NPA) directly grown on a copper substrate by the one-step electrodeposition method is synthesized without any template. Most of the nanoplates with a height of ∼350 nm and length of up to several micrometers stand vertically on the copper substrate. The as-prepared cobalt nanoplates have the {100} crystal facets as the basal plane. By adjusting the electroplating conditions, the morphology and size of the cobalt nanocrystal can be modulated. Owing to the interesting anisotropic nanostructures, remarkable magnetic anisotropy is obtained on the Co NPA. In addition, the cobalt nanoplates are demonstrated to show enhanced magnetic properties compared with other cobalt nanostructures.