The electrochemical deposition of Ag-Pd from acidic nitrate solutions has been studied. Under suitable conditions, phase separation in the form of solid solutions with different compositions is observed at the micron scale. The phase separation is not generated by electrochemical instabilities, but instead is due to a wide difference in the intrinsic reduction kinetics and the distinct nucleation characteristics. At UPD conditions Ag-Pd films could be grown via underpotential codeposition, in close agreement to thermodynamic predictions. At intermediate overpotentials, phase separation occurs due to local concentration gradients generated by mass transfer limitation for Ag and large nucleation barrier for Pd. Under mass transfer limitations, the growth is uniform and the composition corresponds to the prediction based on the ion diffusivities. (C) 2019 The Electrochemical Society.