The motivation for this thesis originated from the Port Environmental Performance Index project (PEPI), which is part of SETS II, initiated and financed by the EU program Interreg. Port environmental issues are usually multidimensional and lead to difficulties for port decision makers to act based on port environmental data coming from large, heterogeneous, multi-numbered data sources. Performance measurement is critical if any organization wants to thrive, and when it comes to ports and environmental performance there is great challenge in the increasing availability of data sets with a huge amount of information, coded in many different features. The challenge for port management in this context is the translation of raw data into useful information that can be used to improve port environmental strategic decision-making processes, detect relevant profiles, understand relationships among operational features and detect environmental measures. As such, integration of the heterogeneous and uncertain information demands a systematic and understandable framework to organize the environmental information and processes to interpret and use in actual port advising or decision-making context. This thesis proposes: (1) an integrated port environmental indicator model which can serve as a strategic tool for port environmental performance management; (2) a multidimensional framework for port environmental management to control and monitor the port environmental process to achieve the overall environmental goals of the port; and (3) a specified strategic approach to guide implementation of port environmental performance measurement. The thesis discusses the proposed multidimensional framework, integrated model, and the related specified strategic approach for implementing port environmental performance. The results will be used by the participating ports in the SETS II project to guide the development, implementation and assessment of the proposed framework and indicators for port environmental performance through the PEPI model with continuous improvement. The Port Environmental Performance Index is an impact assessment tool that is strategic in nature and has the objective of facilitating environmental integration and the assessment of the opportunities and risks of strategic actions in a port environmental development framework. Keywords: PEPI, ports, environmental performance, measuring, strategy, KPIs