This research analyzes the making up and structuring of social networks by expatriates through a retrospective longitudinal analysis. This approach has enabled to identify the professional, environmental and family factors at work in the setting up of the ties, and above all to understand at which moments these factors interfere in the building up of the various networks. Our results show that the professional and family spheres play distinct roles in the network structuring process. The family plays a major part in the establishment of strong ties required for an efficient adjustment. It is also a powerful activator of more heterogeneous ties within open social networks.