With the development of research in economic history, historians are now testing the hypothesis that maritime networks and port cities contributed to the phenomenon of European integration. This essay applies a holistic approach to discuss how the city of Lisbon, located outside the privileged setting of multi-cultural interactions that was the Mediterranean Sea, became appealing to merchants from far and wide in late-medieval Europe. To do so, it examines a whole array of commercial, normative, fiscal, royal and judicial sources from European archives to discuss if it is possible to observe this phenomenon of European integration in fifteenth-century Lisbon.