The mechanism of TiO2 nanoparticles electro-codeposition with nickel is studied. In-situ different electrochemical techniques such as cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and chronocoulometry are used. The nucleation and growth mechanism of nickel in absence and presence of different nanoparticles concentration are analyzed through a mathematical model. The nucleation process of pure Ni system tends to follow the progressive model with three-dimensional fashion, while Ni/TiO2 codeposition follows an instantaneous nucleation model. The presence of nanoparticles on the cathode offers many favorable sites for nickel crystallization nucleation, promote electrodeposition process and change the preferred orientation of nickel to a random one. (C) The Author(s) 2016. Published by ECS. All rights reserved.