Wire arc additive manufacturing (WAAM) is a high-quality technology for producing large and complicated geometries in close proximity to net shape with low-cost production resources, including welding machines and filler wires. It offers the cost-effective fabrication of large-scale metal parts with high deposition. AA5356 aluminum–magnesium (Al-Mg) alloys can reach medium strength without a solid solution and quenching treatment, thereby avoiding product distortion caused by quenching, which has attracted the attention of WAAM researchers. However, challenges during the additive manufacturing of aluminum alloys, such as porosity or poor mechanical properties, can be overcome by using arc technologies with low heat input. This paper presents metallurgical characteristics and mechanical properties of WAAM AA5356 alloy cylindrical components fabricated by gas metal arc welding (GMAW) and cold metal transferred (CMT) arc welding processes. Herein, a comparison between the welding processes and the resulting heat input shows the effect on the resulting microstructure and the mechanical properties of additively manufactured AA5356 parts. Firstly, the influence of heat input on the porosity and microstructural characteristics were analyzed. Subsequently, the effect of heat input on the mechanical properties of the cylindrical components was studied. The cylindrical component produced by CMT process exhibits fewer and smaller pores with finer grains and reduced segregation of β-(Al3Mg2) phases than the GMAW process. The component fabricated by CMT process showed isotropic superior mechanical properties (tensile properties, hardness, and impact toughness) than the component made by GMAW process.