Radiation-induced segregation was studied in a nickel 1 atomic percent silicon (Ni-1Si) alloy after irradiation at ∼525°C with 3-MeV⁵⁸Ni⁺ ions. Postirradiation profiles of alloy composition as a function of depth from the irradiated surface were obtained by standard Auger techniques and ion-sputtering at room temperature. Rapid segregation of silicon toward the irradiated surface was observed. The solubility limit of silicon in nickel was reached at the surface after a dose of only 0.05 displacements per atom (dpa). Segregation continued to increase up to the highest dose (6.5 dpa) investigated. Precipitation of Ni³Si occurred at the external surface and internally on dislocation loops. The experimental results are compared with calculations using the Johnson-Lam segregation model and a set of parameters that was used previously to fit the temperature dependence of radiation-induced segregation in Ni-1Si.