Joining of multi-metallic assemblies such as aluminum and steel sheets using fusion joining technologies is prudent although the formation of intermetallic compounds along joint interface has remained a critical challenge. An advanced, low-power input, gas metal arc process was employed here for joining of aluminum and zinc-coated steel sheets of dissimilar thicknesses in lap-joint configuration. The heat input during the process was restricted by fast responsive current and voltage pulses that allowed a synchronized arcing and short circuiting at a low arc power. The effect of heat input and thermophysical properties of base materials on the bead profile, joint strength, and distortion was studied extensively. The results indicated a rational improvement of joint quality with lowering of the heat input within a restrictive range of processing conditions such as wire feed rate and travel speed. Most importantly, the mixed-metal assembly exhibited different thermal distortions with the aluminum top sheet undergoing greater distortion than the bottom steel sheet due to a higher coefficient of thermal expansion.