The influence of the core-sleeve boundary interface on the mechanical properties and electrical conductivity of the composite all-aluminium wires made of electromagnetically cast Al-0.5 wt. % Fe and Al-1.7 wt. % Fe alloys was studied. For the comparison all-aluminium wires made of same materials were studied as well. Structural analysis was presented by the scanning electron microscopy of the composite all-aluminium wires cross-section, as well as by the fractographic analysis of the failed tensile samples. It was demonstrated that the effect of the core-sleeve boundary increases with the increase in amount of alloying elements in the composite all-aluminium wires components. The core-sleeve boundary in the composite all-aluminium wires acts as a buffer for the deformation thus the amount of the deformation, that otherwise would be distributed gradually in the all-aluminium wires, is distributed uneven between the core and the sleeve of the composite all-aluminium wires, accumulating more within the composite all-aluminium wires sleeve. The major influence of the core-sleeve boundary is noted in yield strength and ductility of the wires, while electrical conductivity and especially ultimate tensile strength remain mostly unaffected.