Electroless deposition of amorphous iron-phosphorus (Fe–P) is investigated. Fe–P is a potential benign alternative for replacing nickel-phosphorus films commonly used in electronics and surface finishing applications. In the present talk, the role of substrate (Cu) activation by palladium (Pd) in enabling electroless Fe–P deposition will be discussed. Specifically, it will be demonstrated that a critical Pd surface coverage is essential for spontaneous electroless Fe–P deposition to commence. Below this critical Pd coverage, the surface is catalytically inactive for Fe–P deposition. A mechanistic model that incorporates surface heterogeneity due to partial Pd coverage of Cu and the effect of this heterogeneity on electrocatalysis of the reductant oxidation reaction during electroless deposition will be presented. Model predictions will be compared to experimental observations of the electroless surface mixed potential to gain insights into the mechanism by which Pd coverage affects the efficacy of electroless Fe–P deposition. Implications of the findings to the optimization of pretreatment and activation processes commonly used in electroless deposition systems will also be discussed.