AlSi9Cu3(Fe) vacuum-assisted high pressure die cast (VPDC) specimens were investigated by experimental fatigue test and fracture mechanics approach. The aims of the investigations were (i) to evaluate the fracture resistance and (ii) to indirectly determine the threshold stress intensity value (ΔKth) of casting alloy in uniaxial tension. The specimens were sorted into two groups: specimens with different size (0.01-0.40 mm2) natural defects, and specimens an additional artificial blind hole. The fatigue strength region was tested at R=-1 stress ratio to 107 number of cycles to fracture. The fracture mechanics approach was applied to study the behavior of the small cracks by Kitagawa diagram, the defect size was taken into account by the Murakami’s (√area) parameter. The fatigue strength values were 104.7 MPa for smooth specimen, 92.7 MPa for specimen with D0.3 artificial hole, and 87.2 MPa for specimen with D0.6 artificial hole at the prescribed cycles, respectively.