The invention provides an aqueous zinc-nickel alloy electroplating composition particularly useful in an electroplating method for depositing a zinc- nickel alloy layer on a substrate, wherein the deposited layer exhibits uniform nickel concentration and good aesthetics across a broad range of current densities. The electroplating composition comprises an electrolyte composition and an organic composition. In one embodiment, the electrolyte composition comprises a zinc ion source, a nickel ion source, a pH buffering agent and at least one additional salt, and the organic composition comprises a Class I nickel brightener, a Class II nickel brightener, an aromatic carboxylic acid, an aldehyde or ketone compound, and a non- ionic or anionic surfactant. The electroplating composition is particularly free of chelators and free ammonium-producing agents.