Stellite 6 is a cobalt-based superalloy which has a good wear and corrosion resistance and retains these properties at high temperatures. In this study, wire and arc additive manufacturing (WAAM based on the GMAW) was employed to deposit Stellite 6 wire on low alloy high strength steel (S355) and stainless steel (AISI 420) plates. One of the main interests of this study is to produce WAAM Stellite 6 deposits with quality comparable with laser deposition. The advantages of the WAAM process include the high deposition rate, high productivity, high material usage, and energy efficiency with low cost. However, superalloy deposition generally requires maintaining a low dilution level to avoid jeopardizing the integrity of the deposit. As a result, it is important to manage the excess heat input during the WAAM deposition process through a parametric optimization of WAAM deposition of Stellite 6 on S355 steel substrates. In this study, a WAAM process window is established to guide the process optimization. The optimization method used in this study has been applied in our previous laser cladding work. The generated process window also shows some correlations among the heat input, bead geometry, and dilution. The effects of heat input on the resulting microstructure, elemental distribution, and hardness were discussed. Dilution, microstructure, and hardness were considered for comparison from previous studies of laser cladding deposits. In addition, the obtained optimal conditions were adapted to apply WAAM deposition of Stellite 6 layers on AISI 420 stainless steel substrates. The XRD result shows that WAAM deposits contain Co-Cr-Fe solid solution (FCC), Cr₇C₃ and Cr₃C₂ carbides, and Co₄W₂C intermetallic compound. The results obtained through this study lay a foundation for future research on the wear properties of WAAM Stellite 6 deposits. This can contribute to further development of automated deposition of Stellite 6 using WAAM process for industrial applications.