Ag-Pd alloy films have been applied as decorative finishing, electrical contacts and electrocatalysis. In this work, we investigate the mechanism of Ag-Pd electrodeposition from simple nitric acid solutions. Electrochemical characterization of this alloy system showed that at intermediate applied potentials, phase separation was observed at the micron scale, while in the underpotential region of Ag and the limiting current region for Ag and Pd, we achieved uniform deposits. The main features of these deposits can be summarized in the following three growth stages: At underpotential region with respect to Ag/Ag+, the Ag-Pd films grow via underpotential codeposition (UPCD), in close agreement to thermodynamic predictions, with a slow deposition kinetics.At intermediate applied potentials, phase separation occurs due to local concentration gradients generated by mass transfer limitation for Ag, and a large nucleation barrier for Pd. This resulted in large composition difference between a Pd-rich phase (~80 %at,Pd) and an Ag-rich phase (~25 %at,Pd). Film formation involves two stages: (1) formation of Ag-rich phase, followed by (2) nucleation and growth of Pd-rich phase, which could be fitted using the Scharifker-Hills model. The large nucleation overpotential and sluggish reduction kinetics of Pd suggest a 3D diffusion field for individual Pd nucleus, resulting in the depletion of Pd2+ at the interface.Under mass transfer limitation, the growth is uniform and the composition corresponds to the prediction based on the ion diffusivities and the constitution of the solution. Using the ratio of the mass-transfer coefficient of Ag and Pd, specific composition of Ag-Pd film could be achieved in the limiting current region of Ag-Pd electrodeposition by varying the ratio of Ag+ and Pd2+ in the deposition bath. Figure: (a) classification of deposition potential regions based on initial cathodic scans of the solutions, and (b) comparison between experimental compositional results and the thermodynamic model calculated with concentration of 1 mM Ag+, Activity of AgPd alloy is derived from CALPHAD data by Ghosh et al. Figure 1