Metallurgical characterization, failure mode transition and mechanical properties in dissimilar resistance spot welds of dual phase steel (DP600) and low carbon steel (MSZ EN 10130) are analyzed. It was found that the fusion zone microstructure contains a complex microstructure of retained austenite, martensite, and bainite. The peak hardness in the heat affected zone of advance high-strength steel was greater than fusion zone hardness due to the higher hardenability of advance high-strength steel compared to fusion zone. Dissimilar DP600/EN 10130 spot welds show the highest trend to fail in pullout failure mode with good mechanical properties. Effects of weld microstructure and fusion zone size on mechanical properties dissimilar DP600/EN 10130 spot welds are analysed.