<p>The effects of external pressure during solidification of A356 alloy were investigated on porosity reduction and microstructural evolution. The pressure was applied by using nitrogen gas in a pressure vessel at 1 and 10 bar levels. Image analysis of castings revealed that the porosity level decreased significantly from 0.885% under atmospheric pressure to 0.299% at 10 bar, representing a reduction of more than 66%. This improvement was primarily attributed to enhanced interdendritic feeding and the suppression of pore nucleation under pressure. While phase composition remained largely unchanged, microstructural refinement, including reduced dendrite arm spacing, was observed under pressurized conditions. EPMA analysis revealed minimal differences in the segregation behavior of Si and Fe between the two pressure conditions. Although Mg showed slight changes, likely due to its higher diffusivity in liquid aluminum. The overall improvement in casting integrity was mainly due to the beneficial effects of pressurization on feeding and solidification dynamics.</p>