Interest in geoheritage research has grown over the past 25 years and several countries have issued laws to encourage improvement and conservation. Investigations on geosites are prevalently carried out on land environments, although the study of underwater marine environments is also of paramount scientific importance. Nevertheless, due to the constraints of underwater environments, these sites have been little explored, also on account of the higher costs and difficulties of surveying. This research has identified and assessed the terrestrial and marine geosites of the Portofino Natural Park and Protected Marine Area, which are internationally famous owing to both the land scenic features and the quality of the marine ecosystem. The goal was to pinpoint the most suitable sites for tourist improvement and fruition and identify possible connections between the two environments. In all, 28 terrestrial sites and 27 marine sites have been identified and their scientific value as well as their ecological, cultural, and aesthetic importance has been assessed. In addition, accessibility, services, and economic potential of geosites has also been taken into account. Both the updated database of terrestrial and marine geosites in the Portofino protected areas and the assessment procedure adopted can become useful tools for the managers of these sites and provide decision-makers with possible strategies for tourist development.