Dissimilar metal welded joints were fabricated between SA508 low alloy and 304LN stainless steel using IN82, IN182, and IN152 as buttering alloys. In-situ tensile testing of the welds demonstrated that the crack initiation and propagation were away from the fusion boundary between low alloy steel and buttering material. The heterogeneities like clustered lath martensite with high dislocation density, Type-I boundary, and Type-II boundary near the interface have a meager role in influencing the tensile properties of the welds. On the contrary, grain structure and second phase distribution in re-solidified buttering alloy played a dominant role in determining the tensile properties of welds. This understanding may pave the way to modify the welding parameters, select appropriate welding consumables, and explore the failure-prone location for such kind of transition joints.