Organizations in the humanitarian relief field increasingly need to look outside their own boundaries and engage in a significant level of inter-organizational collaboration. In studying collaborative processes in the nonprofit context, researchers have used different theoretical approaches to investigate the motivations behind why organizations collaborate. Although these studies have contributed to shed some lights on these collaborative mechanisms, little is still known about the main factors that influence the decision of humanitarian organizations to engage into collaboration especially with regards to the implications of information technologies. In this paper, we explore factors for collaboration among members of the GlobalSympoNet, a network of organizations engaged in humanitarian information management. We analyze data collected through nineteen semi-structured interviews. We identified seven factors that could be grouped into three categories including structural, behavioral and organizational. Our findings also suggest that information technologies alone are not enough to motivate and maintain long lasting collaboration.