River Basin Organisations (RBOs) play a key role in implementing the Water-Energy-Food-Ecosystems (WEFE) Nexus and mobilising finance for its execution within transboundary river basins. Based on 12 interviews, a literature review and insights from the Senegal, Zambezi, and Danube River Basins — case studies in the Horizon 2020 project GoNEXUS — this policy brief examines financing mechanisms, available funding and associated challenges, and provides strategic recommendations to enhance WEFE Nexus financing provided through the EU and other donors.