As an independent oversight institution, the European Court of Auditors (1977) plays a key role in the EU Ethics System. On the one hand, the ECA scrutinizes how the EU uses its money and implements its policies, from the perspective of ‘legality’ (compliance audit) and ‘regularity’ (financial audit), as well as the value-added (performance audit) of EU action. In recent years, the ECA has repeatedly focused its audit work on ethics in the EU institutional system, with key special reports dealing with several relevant issues such as the management of conflicts of interest in EU agencies (in 2012); the ethical frameworks of key EU institutionsEU institutions (in 2019) and the ‘revolving doorsRevolving doors’ problem in the Brussels consultancy sector (in 2022). On the other hand, the ECA itself has had to contend with ethics scandals in its own management and has recently reformed its own ethics infrastructure, with a new Code of Conduct for members coming into force in 2022 and the introduction of an Ethics Committee. This chapter analyses the ‘ethics work’ carried out by the European Court of Auditors. It takes both an outward-looking perspective (on the scrutiny of other EU institutionsEU institutions, and through its role in shaping audit norms), as well as an inward-looking perspective (on internal standard-setting and ethics reforms). The chapter examines the evolution of the ECA’s own ethical guidelines (based on values of independence, integrity, objectivity, transparency and professionalism) and findings of an international peer review (2019) and external appraisal (2022) of the ECA’s ethical framework.