This article looks at the collaboration relations of CEOs during different phases of the integration process into a network by using various proximity dimensions. Based on the life narratives of 21 CEO members belonging to a regional network, our study underlines that three integration phases exist, within which different proximity forms are mobilised. Whereas, institutional, personal and social proximities are significant during the entry phase, temporary geographical and cognitive proximities appear to be essential for building collaboration. Moreover, if social and personal dimensions play essential roles in starting collaborations, we note that social proximity remains less decisive for joint collaborative projects. These results enrich recent debates about the dimensions of proximity. They open lines of thinking about ways to encourage the integration of new members.