Abstract The growth of thin Fe overlayers on Al(110) and Al(001) surfaces has been investigated using high-energy ion backscattering (HEIS) and X-ray photoelectron spectroscopy (XPS), for Fe coverages from 0 to 15 ML deposited at room temperature. For the Al(001) surface, measurements of the backscattered ion yields from Al and Fe atoms show that the Fe atoms do not form a simple overlayer on the Al substrate, but displace Al atoms from their equilibrium positions to form a mixture of FeAl. The inter-mixing continues up to about 5 ML Fe coverage before Fe metal begins to cover the mixed surface. For the Al(110) surface, intermixing of Fe and Al atoms was observed up to about 9 ML Fe deposition, where Fe metal begins to cover the surface. In neither case was Fe diffusion into the bulk Al substrate observed. XPS results show no chemical shift larger than the resolution of our measurements for the Fe 2p core level in Fe aluminides. The variation of the Fe XPS photopeak intensity as a function of Fe coverage also supports the two- and three-stage growth models on Al(001) and Al(110) surfaces, respectively.