The examination of a fractured cavity insert, cooperated die to finish geometry intricate aluminum alloy die-casting product, is described. The dominating failure mechanism in the investigated insert is the combination of thermal fatigue cracking and stress concentration. A visual fractographic examination was performed at the cavity insert and crack initiated at the periphery adjacent to a sharp corner. Detailed scanning electron microscopy observations and energy-dispersive X-ray suggest that the crack growth was facilitated by a number of elements: oxidation of the cracks’ surfaces, filling of cast alloy, and high stress concentration of the sharp corner. The thermal cracks were also produced product around the inside wall of the cooling channel. Similarly, these cracks were also subjected to oxidation and filling with scale deposit and oxide. Finally, the schematic of the cavity insert fracture evolution during die-casting is discussed.