Irrigation drainage and industrial wastewaters often contain elevated levels of toxic anions such as selenate, arsenate, and chromate. Immobilizing the contaminants via reaction with zero-valent iron has been proven to be an effective remediation method. Ultrafine metallic and bimetallic particles were prepared by borohydride reduction of aqueous salt solutions and characterized. Nanosized zero-valent NiFe and iron particles rapidly reduced and immobilized selenate from aqueous solutions. Nearly 100% selenate removal was obtained in 5 h. The data show that, at identical solids concentrations, the use of NiFe particles accomplished 42 and 56% greater removals, respectively, than the use of Fe and Ni particles individually. At low selenate concentrations, the selenium removal rate followed the first-order rate kinetics that shifted to zeroth-order at higher concentrations. The maximum selenate removal (87% in 30 min at a solids concentration of 0.5 g/L) was obtained by bimetallic particles containing 70 at. % iron. High removal capacities were observed at pH lower than 8. A mechanism for the selenate removal has been developed.