The challenge for port developments is to minimize long-term uncertainties associated with port operations, risk of increased costs, and large environmental impacts. The aim of this study is to develop a comparative methodology to assess the sustainability performance of a mixed set of ports (different locations, sizes). This methodology involves ranking various long-term port plans and port vision documents against a set of social, economic, and environmental key performance indicators (KPIs) in order to evaluate and interpret future sustainable port-city development plans. The assessment aims to determine the efficiency and sustainability of each of the case study port plans, relative to other ports. Furthermore, the assessment ranks the considered ports based on comparison of pressures within the ecosystems and society, using publically available data in order to evaluate future changes resulting from these pressures. The classification and ranking of each port have been used to gauge the ability of each port to achieve its sustainability goals for port planning as set out in their port plans. The comprehensive results have been compared with the long-term port plan KPIs to evaluate an array of measures both quantitatively and qualitatively. Most of the highest ranking ports have developed a combination of integrated plans, measures, and regulations for sustainable port developments. This indicates that green-port policies need to be interlinked via social, economic, and environmental dimensions utilizing an integrated approach in order to realize maximum potential and strengthen port processes aimed at developing a sustainable port.