The ultrasonic-assisted laser shock peening (ULSP) technique improves the balance between tensile strength and elongation of aluminum alloys through the combined effects of laser shock peening (LSP) and ultrasonic rolling (UR). The 7075–T6 aluminum alloy was selected as the subject of study, and ULSP treatment was conducted. The metallographic structure, phase composition, surface morphology, microhardness, and residual stress were systematically examined. By analyzing the stress-strain curves, fracture morphology, and the improvement mechanism of tensile properties after ULSP treatment was elucidated. The results show that the ULSP treatment induces a significant grain refinement effect, resulting in a gradient structure comprising a severely refined grain layer, a refined grain layer, and the original coarse grain layer. Furthermore, the ULSP treatment effectively mitigated the issue of increased surface roughness associated with LSP treatment. The surface roughness S_a and profile roughness R_a of the ULSP samples are reduced by 74.0% and 82.3%, respectively, compared to the LSP samples. Benefiting from the grain refinement effect, high compressive residual stress, and low surface roughness, the ULSP samples achieved a substantial increase in tensile strength with only a minor sacrifice in elongation. Specifically, the tensile strength is enhanced by 13.3%, while the elongation is only decreased by 11.7%.