[en] Ni–Co–Se layers have attracted a great deal of attention in the field of solar cells, electrocatalyst water splitting and supercapacitors. Electrodeposition is a simple, convenient and low-cost way to obtain Ni–Co–Se layers. However, until now, the electrochemical kinetics of the Ni–Co–Se system, including its growth and nucleation mechanisms, are still unclear. In present work a NiCoSe₂ layer with a nanosheet structure was electrodeposited in a chloride bath. The electrochemical mechanisms of the Ni–Co–Se system were also studied. It is noted that the electrochemical kinetics of Ni–Co–Se electrodeposition can be influenced by both temperature and electrode material; however, temperature does not change the progressive nucleation process and mixed controlled growth mechanism of Ni–Co–Se. The diffusion coefficient D and charge-transfer coefficient α of the Ni–Co–Se system were calculated. The values of D obtained by cyclic voltammogram and chromoamperometry are close to each other at both 20 and 50 °C, respectively, and increase with the increase of temperature. Moreover, the activation energy E _a was also calculated. Specially, a uniform 3D network-structure NiCoSe₂ layer was electrodeposited on ITO glass at −0.9 V and 40 ∼ 60 °C. The increased overpotential during deposition makes the NiCoSe₂ layer more easily gather together; however, there is no significant effect on the surface morphology of the NiCoSe₂ layer when the temperature is between 40 and 60 °C. (paper)