This paper presents a formalisation of the Event-B formal specification language in terms of the theory of institutions. The main objective of this paper is to provide: (1) a mathematically sound semantics and (2) modularisation constructs for Event-B using the specification-building operations of the theory of institutions. Many formalisms have been improved in this way and our aim is thus to define an appropriate institution for Event-B, which we call $$\mathcal {EVT}$$. We provide a definition of $$\mathcal {EVT}$$ and the proof of its satisfaction condition. A motivating example of a traffic-light simulation is presented to illustrate our approach.