The main aim of this work is to investigate the effects of combinative Ce and Zr additions (0.3 wt% Ce+0.16 wt% Zr; 0.3 wt% Ce+0.27 wt% Zr and 0.3 wt% Ce+0.36 wt% Zr) on the microstructure and mechanical properties in cast Al-Si-Cu-Mg alloy. The microstructures features were investigated by optical microscope, scanning electron microscope and hardness measurements. The microstructural analysis has shown that the increase of Ce and Zr contents increases the volume fraction of intermetallics formed during the solidification leading to grain refinement and changes in silicon morphology of the as-cast microstructure. The intermetallics formed do not dissolve during the solution heating treatment (T6). The mechanical behavior at room and high temperatures (175, 210, 245 and 275°C) was determined from uniaxial tensile tests. The high thermal stability of Al-Si-Cu-La-Ce and Al-Si-Zr-Ti-Mg phases found in microstructure, in particular for the alloy containing 0.3 wt% Ce+0.27 wt% Zr, is responsible for the increase to 6.7% and 5.1% the ultimate strength at 210°C and 275°C respectively, compared with the standard alloy.