The welding of aluminum and its alloys has always represented a great challenge for designers and technologists. The preferred welding processes for aluminum alloy are gas metal arc welding and gas tungsten arc welding due to their comparatively easier applicability and better economy but past research on structural aluminum alloys demonstrated lower mechanical and microstructural properties in gas tungsten arc welds when compared to base-metal (BM), that mainly related to the presence of a tenacious oxide layer, high thermal conductivity, high coefficient of thermal expansion, solidification shrinkage, high solubility of hydrogen, and other gases, in molten state. However, there is a continual emphasis on decreasing the cost or weight of a given structure.Friction stir processing (FSP) is a technique that produces local microstructural modification and, when applied to gas tungsten arc welds, improves the microstructure and corresponding mechanical properties at the weld toe and crown locations. Aluminum alloy AA7075 (Al–Zn–Mg–Cu) is one of the high strength aluminum alloys. Its high strength to weight ratio, together with its natural aging characteristics, makes it attractive for a number of aircraft structural applications. The alloy derives its strength from precipitation of Mg 2 Zn and Al 2 CuMg phases. The aim of the present work is to investigate Influence of friction stir processing on microstructure and mechanical properties of AA7075-T6 aluminum alloy jointed by gas tungsten arc welding. The bare and friction stir processed welds were comparatively evaluated for their microstructural characteristics and mechanical properties. Friction stir processing was found to result in substantial microstructural refinement with fine and uniformly distributed particles. The use of friction stir processing has been found to improve the mechanical and microstructural properties of the welds compared to those of jointed by gas tungsten arc welding of this alloy due to grain refinement occurring in the fusion zone. The friction stir processing at 1600 rpm, 80 mm min -1 improved the tensile strength, hardness and percentage of elongation of 7075-T6 aluminum alloy jointed by gas tungsten arc welding by 14 pct, 66 pct and 300 pct respectively. The hardness of base metal (unwelded parent metal) in its initial T6 condition is approximately 120 VHN. But the hardness of the gas tungsten arc welding joint in the weld metal region center is 60 VHN. In the case of friction stir processed joints, the weld metal hardness has been found to increase compared to unprocessed welds and arrive 90 VHN in friction stir processed weld at welding speed of 80 mm min _1 and rotational speed of 1600 rpm. This work demonstrates that friction stir processing is an effective strategy for improving mechanical and microstructural properties in aluminum–zinc alloy fusion welds. Keywords : Gas tungsten arc welding; Friction stir Processing; 7075-T6 aluminum alloy; Microstructure