The microstructural evolution of the ordered Cu–56 at % Au alloy under plastic deformation has been studied. It has been revealed that under the influence of deformation, the с-domain structure is originally destroyed, and the lamellar structure demonstrates a higher stability under deformation impacts. It has been demonstrated that deformation to 70% leads to the formation of ultrafine-grained two-phase (order + disorder) structure in the alloy. Based on the results of mechanical tensile tests, the deformation behavior of the ordered and disordered alloys has been analyzed. It has been concluded that the mechanical properties of the moderately deformed (to ~20%) ordered Cu–56 at % Au alloy may be of interest for practical applications.