This paper explores the horizontal and vertical separation of powers in the Banking Union in the light of fundamental principles of Union law. Regarding the vertical separation of powers, the allocation of supervisory powers to the ECB might lead to conflicting policy objectives between supervision and monetary policy, and supervision and restructuring. Yet, a different institutional structure for the SSM would not mitigate these concerns. Legal review of the SSM provides some safeguards against such conflicts, but needs to respect the discretionary powers of the SSM. Parliamentary control, however, could be improved; and executive control of the SSM by the Commission might be advisable, though difficult to realize. As concerns the horizontal separation of powers, the rulemaking powers of EBA should be strengthened against the dominance of the ECB. On the whole, however, levelling up the role of the national competent authorities would endanger the objectives of the Banking Union.