This paper presents a comprehensive review of National Single Window concept and its impact on sustainability in maritime transport and seaports. The theoretical frameworks of sustainability, maritime transport, seaports, the National Single Window and the Maritime National Single Window is provided. The importance of stakeholder connectivity in maritime transport and seaports in improving sustainability is demonstrated, as well as the advantages of smoother data exchange through global analysis of National Single Window examples, the majority of which present national and regional best practices and initiatives. Empirical data has been provided in order to demonstrate the impact of National Single Windows and Maritime National Single Windows on seaport sustainability (economic, environmental, and social).