Initiating the Pandemic Emergency Purchase Programme (PEPP) to fight the effects of the Covid-19 pandemic on the monetary policy transmission mechanism, the European Central Bank (ECB) pledged that ‘[t]he Governing Council will do everything necessary within its mandate.’ The question arises: Who holds the ECB to account to verify whether it stayed ‘within its mandate’? This is the core of this research. The PEPP is an illustration that the ECB is willing, and to a certain point, capable to go beyond its non-majoritarian role. Generally, following the so-called ‘global financial crisis’ of 2007, we have witnessed (i) the expansion of the ECB’s monetary tools as it employed unconventional monetary policy; (ii) the establishment of the so-called ‘Troika’, in which the ECB plays a central role by exercising its subsidiary mandate to support to economic policies; (iii) and the development of a new legal construction, namely the ECB’s novel responsibility for banking supervision within the complicated framework of the European Banking Union (EBU). Although the ECB’s accountability is not a new research subject, this research provides insights on this topical subject by looking not only at the legal provisions but also the related practices to keep the ECB accountable. In particular, the research examines five the accountability forums that hold the ECB to account: the European Ombudsman, the European Court of Auditors, the European Parliament, the Administrative Board of Review and the Court of Justice of the European Union. Moreover, the research takes a holistic approach because it assesses the ECB’s tasks in monetary policy, banking supervision as well as economic policy, affecting the ECB’s overall accountability and credibility. This research demonstrates that the legal framework of accountability does not necessarily coincide with the accountability practices. Although the overall accountability of the ECB is not unacceptable, the ECB came to the foreground as the dominant actor in the accountability relationships. Hence, there is room for improvement and Treaty changes are imminent. In the meantime, we have to rely on the responsiveness of the ECB. This is essential for the ECB if it is to regain public acceptance after its role as a political actor since the crises. As a banking supervisor the ECB needs to reinforce its responsiveness while considering the importance of confidentiality. It seems that we have not reached these balances yet.