Silicide formation has been studied in Cr‐Si thin‐film samples by MeV 4He+ backscattering and glancing‐incidence x‐ray diffraction. Samples of SiO2/Cr/Si configuration were prepared by sequential e‐gun deposition of Cr and Si onto SiO2 substrates with the relative film thicknesses adjusted to Cr:Si ratios of 3.0 (Cr3Si), 1.67 (Cr5Si3), and 1.0 (CrSi). In the early stage of phase formation when both unreacted Cr and Si are present, the CrSi2 phase is formed. The phase grows until the Si is completely consumed, and then a metal‐rich phase, Cr5Si3, is formed at the Cr‐CrSi2 interface. Upon further heating of samples with a Cr:Si ratio of 3.0, Cr5Si3 reacts with Cr to form a more Cr‐rich phase, Cr3Si. The CrSi phase was observed only in samples with a Cr:Si ratio of 1. All the compounds present in the phase diagram were observed. The end phases are determined by the availability of Cr and Si in the reactions and can be predicted from the phase diagram.