ABSTRACT This study aimed to develop a methodology for scholars and practitioners interested in facilitating collaboration within organizations crossing disciplines, sectors, and geographic boundaries, also called cross-sector partnerships (XSP). The authors developed a three-stage methodology, called participatory mapping, that supports the development of a XSP's collective identity by recognizing shared goals and the mechanisms to achieve them. The participatory mapping method guides XSP members in mapping, negotiating, and ritualizing elements of their collective identity. Study outcomes align with findings of previous research, yet they also offer new insights. The authors recommend approaching XSPs as ecosystems in constant flux, recognizing how member turnover, and changing projects make living narratives and tacit knowledge critical aspects of XSPs that require ongoing management from dedicated staff.