Dissimilar weld joints are critical to various industrial applications. An important performance measure of the joint is its mechanical properties. In this work, investigations were carried out to understand the effect of post-weld annealing heat treatment on the welded joint of SA312 TP304 stainless steel and SA335 P11 chrome moly alloys formed by tungsten inert gas welding (TIG) and metal inert gas welding (MIG). The microstructures were studied using optical microscope and the correlation between microstructures and microhardness is assessed at the different regions of the joints before and after the heat treatment. The effect of post-weld heat treatment has been observed on the microstructure in all regions of the welds indicated by the alteration in the grain size and formation of precipitates. Subsequently, increase in the hardness is observed in the base metals, heat-affected zones (HAZ) and weld zone of these joints. The maximum hardness was measured at HAZ of SA335 P11 alloy side of the heat-treated specimens. Base metal and HAZ of SA312 TP304 of both TIG and MIG, as-welded joints are characterized by twinned-equiaxed grains of austenite free from grain boundary precipitation, whereas substantial carbide precipitation was observed in these regions after heat treatment. The weld zone revealed dendritic structure comprising of finer metal carbides formed during solidification of weld pool.