Platinum particles deposited via electrochemical methods are frequently inhomogeneous and have poor stability on diamond electrode surface. These problems are solved in this study by applying a two-step deposition route. In the first step wet chemically synthesized Pt nanoparticles are seeded and these seeds distribute homogeneously on diamond surface with sizes around 15 nm in diameters. Electrochemical deposition at a constant potential is then applied to overgrow Pt seeds. The sizes of Pt nanoparticles are controlled by the consumed charge during electrochemical deposition process. The homogeneity, sizes variation, activity, and stability of these Pt nanoparticles on diamond surface are investigated with scanning electron microscope (SEM) and electrochemical techniques. The simulation of electrochemical overgrowth of Pt seeds as well as electrochemical deposition of Pt nanoparticles on diamond is performed, revealing different nucleation processes. The proposed method is promising and useful for depositing other various catalysts on different electrodes. (C) 2012 Elsevier Ltd. All rights reserved.