The two of the most utilized aerospace materials i.e. ultra high strength maraging steel (250) and corrosion resistant, high strength 13-8 Mo stainless steel in solution annealed and cold worked condition have been joined by three different fusion welding processes, namely, Gas tungsten constricted arc welding (GTCAW) and high energy density fusion processes like Electron beam welding (EBW) and Laser beam welding (LBW). The highly popular GTCAW process incorporating inter pulsing technique, was carried out by using the W2 maraging steel filler wire. The dissimilar joints were welded by EBW and LBW processes autogenously without any filler wire. All the dissimilar welded joints were characterized by microstructural observations and validated by mechanical properties in the as welded as well as post weld ageing treatments. Post-weld aging heat treatment conditions have been chosen in such a way that mechanical properties can be optimized with minimal distortion during bulk production. The tensile properties were correlated with microstructure and microhardness profiles. Electron beam welded joint with post-weld ageing cycle of 13-8 Mo stainless steel i.e. soaking at 510 °C for 4 hours followed by air cooling demonstrated the superior mechanical properties amongst the all welds.