This study reports that Zn addition greatly enhances the bake-hardening response of an Al-Mg-Si-Cu alloy. The pre-aged alloy exhibits a high strength increment of 135 MPa after paint baking. Differential scanning calorimetry, atom probe tomography and high-resolution transmission electron microscopy reveal that Zn addition and pre-aging have significant effects on the solute nanostructure formation. Zn atoms partition into solute clusters/GP zones, and reduce the activation energy of beta" precipitation in the alloy. (C) 2015 Elsevier B.V. All rights reserved.