In this work, we studied the effect of the intermetallic compound Al3Er on the structure of the aluminum alloy A–0359.0, its physical and mechanical properties and the nature of destruction. It was shown that the introduction of 0.3 wt. % into the melt A–0359.0 reduces the average size of dendrites and microhardness values, does not affect the density and hardness values, and increases the values of tensile strength and maximum deformations before fracture. The investigated alloys demonstrate a similar deformation behavior, while the fracture surface of the A–0359.0 alloy containing 0.3 wt. % Er, is significantly developed in comparison with the initial alloy.