Abstract: The effect of small copper additives on the microstructure and physical and mechanical properties of an ultrafine-grained Al–1.47Cu–0.34Zr (wt %) alloy structured by high pressure torsion after preliminary annealing at a temperature of 375°C for 140 h is investigated. As a result of processing, high values of strength characteristics are achieved (nominal yield stress of 430 MPa, ultimate strength of 574 MPa) at an acceptable level of electrical conductivity (46.1% IACS) and plasticity (elongation to failure ~5%). Taking into account the micro-structural parameters determined using X-ray diffraction analysis and transmission electron microscopy, an analysis of the acting strengthening mechanisms providing such a high strength is carried out. It is shown that Cu plays a key role in strengthening. The addition of copper contributes to significant grain refinement and, as a result, increases grain boundary strengthening. In addition, doping with copper leads to significant additional strengthening (~130 MPa) in ultrafine-grained alloy, which is not typical for a coarse-grained state. The most probable reasons for this strengthening can be the segregation of Cu at grain boundaries and the formation of Cu nanoclusters.