Recently, the introductions and spread of invasive alien species (IAS) in Europe have increased and different regions are affected by their impact (East and South Europe, Danube Region). Two new regional networks have been created and developed: the East and South European Network for Invasive Alien Species (ESENIAS) and the Danube Region Invasive Alien Species Network (DIAS). Information about the establishment, structure, mission and activities of the two networks is presented. ESENIAS promotes awareness raising and capacity building initiatives at yearly workshops, conducts scientific research and exchanges and disseminates IAS information and research results by the ESENIAS Internet portal (www esenias.org) and by joint publications. The largest project implemented by the ESENIAS countries is the ESENIAS-TOOLS project funded by the Financial Mechanism of the European Economic Area 20092014. Currently, DIAS focuses on the completion of the DIAS strategy and work plan, as well as on the implementation of the Danube-IASapp project funded by the European Commission. The 7th ESENIAS Workshop with Scientific Conference 'Networking and Regional Cooperation Towards Invasive Alien Species Prevention and Management in Europe', co-organised by the Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, ESENIAS and DIAS, was held on 28-30 March 2017, in Sofia, Bulgaria. The scientific outcomes of the Conference are reviewed here under the following topics: 1) Alien species trends in the ESENIAS countries: Introduction and establishment success; 2) Alien species trends in the ESENIAS countries: Range expansion; 3) Vectors and pathways of introduction and spread of alien species in the ESENIAS countries; 4) Invasive alien species traits; 5) Invasive alien species impact in the ESENIAS countries; and 6) Invasive alien species prevention and management.