Multilateral banks play an important role in financing larger investment projects within the EU and in most parts of the world. These institutions are less known than that commercial banks, even though many of these institutions – and in particular, the European Investment Bank – have provided a truly remarkable volume of financial support for the countries where they operate, including EU Member States. This paper introduces the largest of the multilateral financial institutions: the European Investment Bank. It elaborates on the specific regulatory framework applicable to its structure and operation as well as a number of special characteristics affecting this institution exhibiting a unique dual nature: a multilateral bank and an EU institution. This paper examines the complexity of the EIB’s operation, in particular, the impact of external circumstances such as EU enlargements of the past and the Brexit issue in the present. Beyond these specific questions, generic issues relating to its operations, governance, the applicable specific prudential requirements and the non-supervised nature of multilateral financial institutions are analyzed as well. This paper also reflects on the EIB’s unimpeachable role in financing the EU economy and on its pioneering role in bringing non-financial considerations, such as environmental protection into the implementation of financial operations.