This study aims to analyze the effect of varying filler types, namely ER5356, ER4043, and ER5183, on the microstructure, tensile strength, and hardness of Aluminum 6061 welded joints using the Gas Tungsten Arc Welding (GTAW) method. Aluminum 6061 was selected because it offers a combination of lightweight properties, corrosion resistance, and good mechanical strength, making it widely used in the transportation, construction, and manufacturing industries. However, the welding process can cause changes in the microstructure that affect the mechanical properties of the welded joints.This study was conducted experimentally using Aluminum 6061 as the base metal and three different filler types, namely ER5356, ER4043, and ER5183. The tests performed included microstructural observations in the Weld Metal (WM), Heat Affected Zone (HAZ), and Base Metal (BM) regions, tensile testing based on the ASTM E8 standard, and Vickers hardness testing to determine the hardness distribution across the welded joint.The results showed that variations in filler type affected the microstructural characteristics and mechanical properties of Aluminum 6061 welded joints. Differences in the chemical composition of each filler resulted in different microstructural morphologies, which consequently affected the tensile strength and hardness values. The ER5183 filler produced the highest tensile strength and a more homogeneous microstructure compared with the other fillers. In addition, magnesium-based fillers demonstrated better mechanical properties than silicon-based fillers. Based on the results, it can be concluded that the selection of filler type significantly affects the quality of Aluminum 6061 welded joints, with ER5183 providing the best performance in terms of joint tensile strength.