In this study, the characterization of a welded joint between structural steel, S275JR, and austenitic stainless steel, X2CrNiMo17-12-2, was performed. The theoretical section outlines the classification of steels, with a particular focus on structural steels and austenitic stainless steels. It covers the techniques used for joining steels, describes welding as the most commonly used method, and lists the basic welding processes. The weldability of structural steels and austenitic stainless steels is discussed, as well as the tests conducted to characterize the welded joint. In the experimental section, tensile testing, bend testing, hardness measurement (HV0.2 and HV10), and macrostructural and microstructural analysis of the welded joint that performed by manual arc welding with a coated electrode, were performed. It was found that the welded joint has satisfactory tensile strength. During the bend testing at an angle of 180°, no defects were observed on the critical surface of the weld face and root. In the heat-affected zone, on both sides of the welded joint, an increase in HV10 hardness and HV0.2 microhardness was observed, with the highest hardness values measured in the weld metal. The welded joint exhibits a regular geometry and a clearly defined fusion line. The microstructure of the base material, S275JR steel, consists of ferrite and pearlite, while in the stainless steel X2CrNiMo17-12-2, in addition to austenite, delta ferrite is also present. In the heat-affected zone, on the structural steel side, grain growth and an increase in the amount of pearlite were observed, while on the austenitic stainless steel side, the volume fraction of delta ferrite increased. In the center and root of the weld metal, which has a typical cast microstructure, very small pores were observed in places.