Massive international response to humanitarian crises such as the South Asian Tsunami in 2004, the Hurricane Katrina in 2005 and the Haiti earthquake in 2010 highlights the importance of humanitarian inter-organizational collaboration networks, especially in information management and exchange. Despite more than a decade old call for more research on the effectiveness of inter-organizational networks in the nonprofit context, to date limited work has been done. The objective of this dissertation is to develop a theory that provides a better understanding of organizational and network effectiveness in the humanitarian relief field. The study deals with two broad research questions. The first research question focuses on the relationship between network structural characteristics and network effectiveness. The second research question concerns organizational effectiveness and focuses on the relationship between organizational internal characteristics (and especially the availability of information technology), ego-network characteristics, network structural characteristics and effectiveness. To answer these research questions, I used a multi-method research design that applies social network analytic techniques in combination with statistical analyses (correlation and regression) and content analysis to analyze data collected through multiple sources including a web-based survey, semi-structured interviews, and database search. At the network level of analysis, my findings extend a previous model for assessing network effectiveness in the humanitarian relief field. At the organizational level of analysis, my research proposes an integrated approach for assessing effectiveness that takes into account the characteristics of organization but also those of the network in which the organization is embedded. My study also highlights the catalytic role of information technology on organizational effectiveness in humanitarian information management and exchange. The dissertation concludes by highlighting both theoretical and practical contributions and by suggesting directions for future research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]