The process of mechanical alloying in the 33Al-45Cu-22Fe (at.%) powder mixture subjected to high-energy ball milling was studied. Due to complexity of the alloy formation in this system, several methods – X-ray diffraction phase analysis, Differential Dissolution, thermal analysis and Transmission and Scanning Electron Microscopy – were combined to obtain the detailed information on the structure and composition of the mechanical alloying products. Possible formation mechanisms of these phases during mechanical alloying are discussed. No crystalline phase containing Fe and Cu, Al has been found in the products of mechanical alloying of the 33Al-45Cu-22Fe mixture. The formation of Cu-Al phases followed the sequence of Al2Cu → Al4Cu9 → Cu(Al) solid solution. When only those phases that were detected by the XRD analysis were taken into account, the mass balance of Al and Fe in the products of mechanical alloying was not satisfied. The Differential Dissolution and high-resolution Transmission Electron Microscopy data suggest the formation of non-stoichiometric X-ray amorphous phases containing all three elements. Reasons for the retardation of the solid-state interaction between aluminum and copper in the ternary powder mixture are discussed.