Given the increased numbers of disasters and humanitarian crises which occur in the face of diminishing global resources, the contemporary disaster management and humanitarian fields face greater challenges to optimize cooperation and coordination processes among actors as well as in ensuring and increasing humanitarian aid delivery performance. This research, by using two case studies, will comparatively investigate inter-organizational cooperation and its performance on humanitarian operations during emergency response periods of the West Java Earthquake 2009 and the West Sumatera Earthquake 2009 in Indonesia. A combination of quantitative analysis, social network analysis (SNA), and qualitative analysis is used. SNA has been proven to be instrumental in modeling humanitarian actors’ cooperation. In this research, humanitarian operation performance is analyzed in terms of its coherence, coverage, and connectedness. By categorizing results from the SNA in correlation with Gillmann’s typology, it is proven that the networks in West Java fit the lead-agency type while in West Sumatra fit the lead-partnership type. In terms of performance, humanitarian operations in West Sumatra performed better in all three criteria compared to those in West Java. Based on the conclusions from this research, recommendations to improve cooperation and coordination among humanitarian actors in disaster situations have been made.