The Basel III Accord on a ‘Global regulatory framework for more resilient banks and banking systems’ was issued in late 2010 as the cornerstone of the international regulatory response to the global financial crisis. Its adoption into European Union (EU) legislation has, however, been met with considerable member state reticence and intra-EU negotiations are ongoing. This paper investigates the political economy of new capital requirements in the EU, arguing that the institutional features of national banking sectors convincingly account for the divergence in EU member state preferences on capital rules.