Tensile tests with 3D in-situ observation were performed using X-ray tomography on a solution heat treated Lost Foam Cast A319 alloy. In-situ tensile testing allowed crack initiation and propagation to be visualised in 3D whilst the digital volume correlation technique was used to measure 3D deformation fields. Crack initiation mechanisms and the evolution of damage during crack growth together with the localized strains at the onset of cracks were studied in 3D. The results show that cracks initiate at hard inclusions, i.e. eutectic Si, iron intermetallics and Al2Cu intermetallic phase, in the vicinity of large pores under the influence of their strain concentration. Once initiated, cracks appeared to preferentially grow through the cracked hard inclusions. Quantitative analysis revealed that the average strain level for the failure of iron-intermetallics exhibits lower value than for Al2Cu intermetallic phase. Besides, final fracture was more prone to occur at Si phase, iron intermetallics and Al2Cu intermetallic phases than Al dendrites. For the various hard inclusions, failure predominantly occurred by fracture rather than decohesion.