In 2001 the National and University Library (NUK), in co-operation with the International Federation of Library Associations and Institutions (IFLA), organised the conference ‘Providing Access through Co-operation’, which focused on inter-lending and document supply. In addition in 1999 the NUK co-operated with the Goethe-Institut and the French Cultural Institute Charles Nodier, Ljubljana to organise a conference on ‘Public Libraries in New Europe in the Context of Social and Economic Change - Influences on the Construction of Library Buildings.’ France Bevk Goriška Library, Nova Gorica co-operates regularly with the Biblioteca statale Isontina from Gorizia in Italy; they jointly organise exhibitions and exchange materials. France Bevk Goriška Library has also organised an international workshop on ‘the Role of Public Libraries in Local Communities.’ The NUK regularly co-operates with the Czech National Library, and also with the National Libraries in Albania, Bosnia and Herzegovina, Croatia, Macedonia, Hungary, the Russian Federation and Serbia, exchanging library staff over varying time periods. The Oton Župančič Library collaborates with several libraries. Its staff have participated as mentors in a programme involving Albanian libraries and in co-operative projects involving the Gradska Library in Rijeka (Croatia), the Municipal Library in Helsinki (Finland) and the travelling library service of Tampere Library (Finland).

Slovenia currently has five libraries which deal with international inter-library loans - the National and University Library (NUK), the University of Maribor Library, the Central Technological Library, University of Ljubljana, the Central Economics Library and the Central Medical Library. These use international lending services such as BLDSC, BLSRIS, TU Delft, Subito, Ann Arbor, GBV, ArtTEL and Blaise Line. Slovene libraries currently borrow around 10,000 documents a year, however inter-library lending is very expensive for the user. Exchange of publications at NUK currently involves 145 libraries and other organisations from all over the world.

The NUK, along with other European national libraries, takes part in various international projects which are co-funded by the European Commission: The European Library (TEL), co-ordinated by the British Library along with eight other European national libraries and the Conference of European National Librarians (CENL); Linking and Exploring Authority Files (LEAF); INKCOR (Ink Corrosion); and the PAPYLUM, EUREKA 1681 project (laser cleaning of paper and parchment). The Central Technological Library, University of Ljubljana has participated in COPERNICUS within the framework of the project EISS-CEE/NIS (Establishment of Electronic Information Services in the countries of CEE and the New Independent States).

Slovene libraries are members of various international or foreign organisations and participate in their work. These include the International Federation of Library Associations and Institutions (IFLA), FID, ALA, LIBER, CENL, COBRA Forum, the European Commission on Preservation and Access (ECPA), ELAG, NGA, the UK Serial Group, CIB, IBBY, the Consortium of European Research Libraries (CERL), Blue Shield, the United Nations Educational, Scientific and Cultural Organisation (UNESCO) and the Alpe-Adria Group. Librarians of the NUK are members of various international standing committees relating to cataloguing, statistics and bibliography. They take part in organising workshops and open sessions. They are also members of various executive boards, including CENL, COBRA Forum and ELAG. One Slovene librarian is a member of the European Commission on Preservation and Access (ECPA), which has its headquarters in Amsterdam.

In 2006 NUK co-operated, either as leader or partner, in 10 international research projects, mainly financed from EU funds – these are E-Books on Demand (EoD), the European Digital Library (EDL), reUSE (an E-content programme), Web Cultural Heritage (Culture2000), TEL-ME-MOR, PaperTreat and SurveNIR. Two EU-funded projects - Web Cultural Heritage and reUSE - were successfully completed.

In October 2006 a meeting of the Federation of European Publishers (CENL/FEP) working group was organised at NUK in Ljubljana. As a TEL-ME-MOR project partner, NUK also organised also a two-day regional expert workshop in May 2006, with participants coming from 11 countries. The workshop discussed research requirements in the new member states and possible ways of improving access to cultural and scientific resources, stimulating greater participation of organisations in future EU-funded research projects, and the utilisation of TEL-ME-MOR results in the creation of national policies.