As manager of a World Heritage site the Trilateral Wadden Sea Cooperation (TWSC) cooperates closely with UNESCO and its World Heritage Centre (WHC), predominantly within the framework of the UNESCO programmes Marine World Heritage and World Heritage and Sustainable Tourism. As Secretariat of the Agreement on the Conservation of Seals in the Wadden Sea (WSSA), the Common Wadden Sea Secretariat moreover works closely together with the UN Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention; CMS).
The World Heritage Centre highly encourages sites to create partnerships between each other – a philosophy that has been part of the TWSC since the 1980s. The Cooperation has established collaborations with other coastal wetland areas as well as other natural World Heritage sites around the world. Among such sites are the Getbol wetlands in the Republic of Korea, the National Park Banc d'Arguin in Mauritania and the Wash-Northern Norfolk Coast in the United Kingdom.
Within the European Union the Cooperation has been involved in transboundary INTERREG projects. The current projects are Building with Nature, Nakuwa, Waddenagenda and PROWAD LINK.