A method for controlling the shapes and sizes of Cu nanoparticles during electrodeposition has been developed by tailoring the surface morphologies of TiN-coated electrodes. Larger octahedral Cu NPs grew on a granular TiN film; smaller, irregular Cu NPs formed on a pyramidal TiN film. The surface morphology of the TiN film affected the accumulation of Cu2+ and hexadecyltrimethylammonium (CTA(+)) ions, leading to the different shapes and sizes of the resulting Cu NPs. The significant steric effect of the CTA(+) ions was confirmed when using the film of pyramidal TiN as the electrode in the CTAB-containing electrolyte; it contributed to the growth of the smaller, irregular Cu NPs. The sensitivity of the smaller, irregular Cu NPs in the detection of glucose was better than that of the larger, octahedral Cu NPs because of the former's greater increase in the Cu2+-to-Cu-0 ratio.