This chapter provides a comparative constitutional analysis of the ECB’s mandate with a view to understanding the role undertaken by this and several other important central banks during and after the great financial crisis (GFC). It discusses the relationship between a central bank’s mandate, its objectives, and tasks, in law and in action. Moreover, it gives an overview of both the formal mandate of the ECB, the FED, the Bank of Canada, and the Bank of England, and how these formal mandates have been implemented. Statutory sources remained mostly unchanged whereas policy actions have reshaped the practical scope of central bank mandates. Monetary policy strategy implements central bank mandates through extra-statutory sources, taking advantage of the flexibility granted to the central bank by their frameworks. The common analytical grid of single versus dual mandate may be revisited, giving full credit to a different macroeconomic environment and interactions with other public policies.