A two-stage solution treatment composed of an initial soaking at 420 °C for 10 min and the second soaking at 500 °C for 10 min was applied to cold-worked AA6063 aluminum alloy samples after equal channel angular pressing (ECAP) for two and four passes. The microstructures and mechanical properties of the samples were compared with those of the samples after a routine one-stage solution treatment at 500 °C for 10 min. Abnormal grain growth (AGG) occurred to the samples during the one-stage solution treatment. However, no AGG was observed in the samples after the two-stage solution treatment. As a result of the prevention of AGG from occurring, the hardness, yield strength and ultimate tensile strength of the alloy after the two-stage solution treatment were significantly increased, while elongation to failure remained almost unchanged.