This study examined whether there are empirical evidences of organizational learning in the U.S. emergency response system and how the strategic uses of lessons enabled organizations to upgrade system's capabilities and interaction structure to respond to major disasters. For this, this study conducted comparative analysis of Hurricane Katrina and Gustav response systems and analyzed data from semi-structured interviews with the managers of 36 leading organizations that actively participated in both response systems. To address challenges from complex and uncertain circumstances of disasters, organizations need to collaborate and their joint operations should be nicely coordinated. The findings of this paper reveal that, through effective communications, organizations could secure timely, accurate, and valid information and create a common knowledge base that is critical for collaborative response to disasters. In addition, organizational capacity to detect, process, and transmit information could increase through appropriate training and retention programs. Importantly, the collective capacity of organizations to collaborate in coherent ways could be strengthened through the development of organizational culture that facilitates face-to-face interaction.