Pre-print, Working paper: Regional integration affects location decisions of MNCs and therefore influences each member country's provision of investment incentives, which in turn may trigger relocation. As a consequence, subsidy competition increases as integration proceeds. We analyze the welfare consequences of this phenomenon, modelling subsidization as a game between a MNC facing different location alternatives and governments that may deter or induce relocation by means of subsidies. We show that the combination of integration and subsidy competition may lead to an excess of subsidization. We also discuss how the interest of harmonizing subsidies, the net gains from integration crucially depend on technological differences, ownership and the absorption capacity of MNC profits by countries. Lastly, we find that the gain from supranational subsidy coordination increases with integration.