ABNT 4140 steel is used in the manufacture of gears, shafts and molds and must provide good resistance to fatigue and wear. Therefore, the study of its properties is of significant interest. In this work, the microstructures, and mechanical properties of ABNT 4140 steel, salt bath nitrided at 570 °C for 4 h, and hot rolled, were investigated for comparative purposes. The samples were characterized by optical, scanning electron and atomic force microscopy, and X-ray diffraction. It was verified, in the salt bath nitrided samples, the presence of white layers, with Fe _2-3N phase and porosity, and diffusion layer. It was possible to measure the effective depths of these layers upon the Vickers microhardness test. In the wear tests, the pin on disc method was used to evaluate the coefficient of friction, volume losses, and the coefficient of wear, for loads of 5, 50 and 100N, dry, at sliding speeds of 0.2 and 1.0 m/s. All tests were carried out at room temperature, with ABNT 4140 steel discs, salt bath nitrided and hot rolled, both sliding against a counter body ball (pin) of ABNT 52100, steel. The salt bath nitriding process of AISI 4140 steel presented poorer mechanical properties such as decreasing of its ultimate tensile strength, ductility, and plasticity, as well as an increase in the average roughness compared to hot-rolled ABNT 4140 steels. The pin on disc tests, with salt bath nitrided samples, resulted in a lower coefficient of friction and worn volume resulted, with more intense oxidative wear mechanism taking place at higher sliding speed.