The energy and environmental policy carried out by the Port System Authority of the Strait (AdSP), in charge of the management of the ports spread along the Strait of Messina, is reported. The Environmental and Energy Planning Document of Port Systems (DEASP, the Italian acronym) is the document explaining the AdSP sustainable strategy to reduce GHG emissions. It defines specific measures, in order to improve energy efficiency in buildings and infrastructures, promote the use of renewable energy in the port area, and confer environmental benefits for the citizens of neighboring territories and port users. The main actions developed are as follows: photovoltaic solar plants and tidal energy systems, electrification of the docks to allow the shore supply of ships, and the construction of a Liquefied Natural Gas (LNG) storage plant to replace more polluting marine fuels, together with awareness campaigns on “green” issues, involving the 3 million users of these ports. Starting from the socio-economic and environmental analysis of the territorial context managed by AdSP, the DEASP analyses all the activities carried out inside port areas and reports the energy consumptions of the concessionaries, in the way to calculate the carbon footprint and develop an environmental sustainable strategy to reduce pollutant emissions. The interventions foreseen are assessed through the cost-benefit analysis and allow reducing the GHG emissions in 2030 up to 46%.