In this study, AISI 2304 duplex stainless steel sheets were joined with AISI 430 ferritic stainless steel sheets via resistance spot welding using various welding parameters. Welding processes were carried out at electrode forces of 0.6 and 0.8 MPa, welding currents of 2 and 3 kA, and welding times of 10, 20, and 30 cycles, and the effects of the welding parameters on the welded joints were investigated. In order to determine the strength of the welded zones, tensile-shearing tests were applied. The weld nugget diameters were measured using a digital caliper, while a micrometer was used to measure the electrode penetration depth values. In addition, hardness tests and scanning electron microscopy (SEM) studies were done on the welded regions of the joined samples. From the measured weld nugget diameters and electrode penetration depth values, it was determined that the changes in the welding parameters affected the weld nugget diameter and electrode penetration depth. The results of the tensile-shearing experiments showed that the increases in the welding parameters were effective on the tensile-shearing strength and weld nugget rupture form. Increasing the welding parameters also resulted in increased weld zone hardness. The microstructural examination indicated in particular that the increases in the welding parameters caused the ferrite grains to grow due to the rise in heat input.