The Mediterranean cities of Cagliari (Italy) and Alicante (Spain) are historical settlements with a long tradition of ports and share many cultural, economic, social and urbanistic characteristics. Port systems lie at the heart of political interests and strategies, technological development, migration, the movement of goods and people, and are heavily influenced by market transformations and spatial modifications, which are often radical. This also involves changes to the morphology of port cities and their surrounding areas, which are dynamic, cosmopolitan and open to change by their very nature. This article aims to identify common urban features, both historical and contemporary, through a comparative study of the urban evolution of the two cities over the centuries. Based on an analysis of surviving graphic and written documentation, the study reveals interesting insights into the current urban morphology of these cities and their approach to urban projects at the interface with the sea.