Electric discharge machining (EDM) is one of the effective nontraditional machining (NTM) processes. EDM has an effective influence on the aerospace and automobile engineering industries and has various applications. This paper aims at investigating the process parameters of the EDM process when machining duplex stainless steels. These steels are a family of grades combining good corrosion resistance with high strength and ease of fabrication. Their physical properties lie between those of austenitic and ferritic stainless steels but are generally closer to those of ferritic stainless steels and carbon steel. In this investigation, process parameters Pulse on Time, Pulse off Time, and wire feed were considered to achieve output responses of better material removal rate (MRR) and good surface quality (Ra). Experiments were designed (L27) using Design of Experiments (DOE) of Taguchi, and process parameters were optimized using the TOPSIS method of optimization.