The shielding gas used in welding processes has properties that can affect the operating characteristics of electric welding arcs. Characteristics such as welding voltage, heat input, and thermal profile, which in turn affect weld geometry, are strongly influenced by the properties of the gas used. Thus, this work aimed to evaluate how preheating the shielding gas influences the gas tungsten arc welding (GTAW) process. For this, a heating system was developed that allowed the variation and control of the gas exit temperature during the tests. A methodology for studying the electric arc was proposed, evaluating the voltagecurrent, profile, and luminosity values. Autogenous welds were performed on carbon steel plates with different gas temperatures, and penetration and width were observed. The results showed that the use of gas preheating influenced the characteristics of the arc and, consequently, weld geometry.