Mechanical alloying (MA) was used in the investigation of the Fe–Zn binary system, which, in the equilibrium state, exhibits negligible mutual solid solubility at room temperature. The formation of single-phase bcc solid solutions with a nanometer-scaled microstructure was achieved by MA in Fe_100−xZn_x (x≤65) powder mixtures. The nearest neighbor distances of these Fe–Zn solid solutions obey the linear relationship given by the Vegard’s law for ideal solutions, suggesting that the solid solutions formed by MA are homogeneous. The average lattice volume expansion also linearly increases to about 13.4% at 65%Zn. At elevated temperatures the nanostructured solid solutions undergo phase transformations yielding intermetallic compounds. The mechanisms for the phase formation in the Fe–Zn system are discussed.