UNEP has played a major role in the establishment of major multilateral environmental agreements (MEAs) dealing with diverse issues from biodiversity, chemicals and hazardous waste to migratory species, ozone depletion (including its funding mechanism), regional seas and trade in endangered species.

Some Multilateral agreements are administered by UNEP, including:

1. Vienna Convention for Protection of Ozone Layer (Ozone Secretariat) and the Montreal Protocol on Substances that Deplete the Ozone Layer (and in addition, the secretariat of the Multilateral Fund for the implementation of the Montreal Protocol is co-located with UNEP)
2. Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
3. Convention on Biological Diversity.
4. Convention on Conservation of Migratory Species of Wild Animals, which includes Agreement on Conservation of African-Eurasian Migratory Waterbirds, Agreement on Conservation of Populations of European Bats, and Agreement on Conservation of Small Cetaceans of Baltic and North Seas.
5. Basel Convention on the Control of Transboundary Movements of Hazardous and their Disposal.
6. Stockholm Convention on Persistent Organic Pollutants (POPs).
7. Rotterdam Convention on the Prior Informed Consent, Procedure for Certain Hazardous Chemicals and Pesticides in International Trade (secretariat shared  with FAO)
8. Regional Seas Programme (Administered by UNEP)

While UNEP hosts the secretariats of these conventions, each of them has its own governing body and political autonomy.

UNEP plays a critical role in creating meaningful synergies between MEAs. It also provides technical, substantive, legal and policy support to enhance the implementations and enforcement of the agreements at the national, regional and international levels.