The first union at the EUI was founded on 2 May 1977, as a branch linked to the Brussels division of the Union of European and International Civil Servants (SFEI).

Thanks to the signature of a framework agreement, the Institute officially recognised the organisation as being representative of the administrative and academic staff. The right of association is also recognised under Article 24b (Title I) of the Statutory Rules for Administrative Staff.

Later on, following developments of the Unione Italiana del Lavoro (UIL) at Ispra, and upon joining the European public service union (Union Syndicale), the US-IUE Florence was established.

US-IUE Florence defends the trade-union liberties of its affiliates, members of the EUI administrative and academic staff.