Archaeological excavations carried out at the ancient Sommer Warehouses, in Lisbon (Portugal), have allowed the identification of a complex phasing related to the Iron Age occupation, incorporating distinct construction phases. In this study, architectural, stratigraphic, and material data from the earliest moments of this occupation (phases II to IV) are analysed. Their chronology seems to span from the second half of the 8th century BC to the beginning of the following century. Elements of both defensive and port-related character were identified. The associated archaeological material is significant, including handmade ceramics and wheel-thrown vessels, with possibly an exogenous origin for the latter. This constitutes a body of evidence of great importance in the context of urban archaeology in Lisbon, allowing for a characterization of the early moments of Iron Age occupation.