Nowadays, the automotive industry is increasingly emphasizing lightweight structures to enhance fuel efficiency, vehicle performance and comply with emission regulations. Traditionally, reducing steel-sheet thickness and boosting strength has been the go-to method for weight reduction, but this approach often compromises panel stiffness. To address the same, there is a growing interest in replacing steel with lighter materials like aluminium, which offer comparable structural properties. AA7075, an aluminium 7000 series alloy with high strength, prepared with precipitation hardening, is one alternative. However, it is regarded to be difficult to join 7075 plates by conventional fusion-welding methods. Friction stir welding, being a solid-state joining process, is proved as a viable technique to join successfully these high-strength alloys, in particular, AA7075. However, the friction stir welding causes reductions in weld properties, and the reduction is more pronounced in thick section welds. Double-side friction stir welding is considered as one of the possible solutions to address the problem of weld-property reductions. In the present study, 6.35 mm-thick AA7075-T651 plates are friction stir welded from both sides. Mechanical properties of the welded joints are evaluated using tensile tests as per ASTM B557 standards and hardness tests. Furthermore, the weld microstructures are also examined using optical microscopy. Higher hardness values occur in weld nugget, and the heat-affected zone records lower hardness values. The weld zone has exhibited joint efficiency of 67% in terms of yield strength, and the tensile fractures are found to take place in the weld nugget. Weld nugget region of friction stir weld exhibits fine equiaxed, recrystallized grains, while heat-affected zone is seen with marginal grain growth.