The Working Group on the Introductions and Transfers of Marine Organisms (WGITMO) has contributed several major achievements to the ICES vision, including the first ICES Viewpoint on Biofouling and its source document, two Cooperative Research Reports, and numerous publications related to ToRs, and the continued population of the AquaNIS database. During the three-year cycle (2017–2019), the scientific experts of this working group, representing 21 countries, met and worked collaboratively with PICES, CIESM and other ICES working groups and international organizations. They have focused their scientific understanding of marine ecosystems to provide information (e.g. national reports, contributing to the AquaNIS database, ToR a), knowledge and advice on the introduction and transfer of marine organisms. This work has primarily concentrated on the following areas: climate change as a factor in invasion success (particularly in the Arctic ToR b); biofouling as a vector for introduction and spread (ToR c), and impact (ToR d); evaluating molecular tools for detection and monitoring (ToR e); and providing ecosystem overviews on non-indigenous species as requested (ToR f). The Group also addressed a request for information on ship-mediated introductions of harmful algal bloom species in the Arctic from the Working Group on Harmful Algal Bloom Dynamics (WGHABD) and presented this work at the WGHABD annual meeting (2018). The first ICES Viewpoint and the source document on biofouling (Galil et al. 2019) were developed as a result of the theme session for the 2017 ICES ASC on bioinvasion trajectories and impacts in contrasting marine environments, organized by WGITMO as a collaboration between ICES-PICES-CIESM. One of the recommendations from that session was to “prioritize investigation on one of the most important non-native species transfer pathways – hull fouling and niche areas, both on commercial ships and recreational vessels, and through this contribute to IMO request for scientific information on use and effectiveness of IMO Biofouling guidelines globally”. Next steps for the WGITMO, jointly with the ICES/IOC/IMO Working Group on Ballast and Other Ship Vectors (WGBOSV), is submitting the ICES Viewpoint and source document to the IMO as a “substantive document” (an action paper, as well as an information paper) to the February 2020 meeting of the Pollution Prevention and Response Sub-Committee (PPR 7). Recommendations from 2017 ICES ASC session also included development of applications of molecular methods (e.g. e-DNA), including the study of genetic structure of non-indigenous species populations (e.g. early warning). Members priorized the use of molecular tools as a potential technology for early detection and monitoring of non-native species at a half day joint session (WGBOSV) in 2018. This ToR (e) was added following that meeting in recognition of the immediate importance of this issue. The Terms of Reference for a working group and workshop on molecular method tools for detection and monitoring to provide recommended guidelines for this rapidly emerging multifaceted tool will be finalized at the next shared day meeting of the groups (WGITMO, WGBOSV), with WGHABD in Poland in March 2020. The WGITMO will seek a continuation of the existing group and modifies the previous ToR for utilization of DNA- and RNA-based molecular approaches to provide science-based tools for strategic planning, policy development, and operational processes regarding non-native species and biological invasions. Two new ToRs are drafted based on member priorities and concerns regarding introduction and transfer issues. One new ToR will address the ecological impact of marine litter as a vector for introduction and spread of marine non-indigenous species. A second new ToR addresses interactions of aquaculture and the environment as it relates to the introduction and spread of non-indigenous species and the risk posed by NIS including pathogens.