Main purpose of present study is to investigate influence of single stage & multistage solutionizing heat treatment on A319 alloy. Aluminium castings are prepared by using the stir casting method. One set of specimens were solutionized at 495 °C/2 h and second set of samples were solutionized 495 °C/2 h and 520 °C/4 h followed by hot water quenching at 60 °C to avoid formation of thermal residual stresses. Quenched samples were age hardened at 100 and 200 °C for different time intervals. The results showed that the specimens with multistage solutionizing heat treatment exhibited 60-90% and single stage solutionized samples showed a 20-30% improvement in hardness when compared to the untreated specimens aged at 100 and 200 °C respectively. Scanning electron microscope and energy dispersive X-ray analysis also confirmed presence of undissolved secondary precipitates during solutionizing heat treatment and effect of multistage heat treatment on enhancement of hardness during age hardening treatment.