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In this study, the AA7075 aluminum alloy plates were joined by a friction stir–welding (FSW) method. Then, the effects of aging and burnishing treatments on the mechanical and microstructural properties of the joints were examined. First, the Al-7075 parts were joined with this method, and then only burnishing, only aging, and aging-plus-burnishing treatments were applied to the FSW specimens. The tensile and bending strengths were examined for all test specimens. Moreover, microhardness measurements and microstructural analyses were performed after all processes. It was seen that the aging and burnishing processes each had an improving effect on the mechanical properties of the stir-welded zone. The results also showed that the combined application of these two methods (aging plus burnishing) had an adverse effect on the parts joined with FSW. Furthermore, according to X-ray diffraction analyses, precipitates, such as magnesium silicide (Mg₂Si), magnesium-aluminum-copper, and copper dialuminide (Al₂Cu) as well as aluminum oxide formations, were observed at the weld region. Among these precipitates, while bending strength improved because of the Mg₂Si formation, formation of Al₂Cu precipitates adversely affected both tensile and bending strengths.