Crisis management has become one of the most important public policy areas in recent decades with greater numbers of manmade and natural disasters. History showed that well-implemented crisis management policies can save lives and reduce costs in a disaster. Literature offered various suggestions for more effective crisis management policies with different techniques utilizing different theoretical frameworks. Informal relationships among crisis management employees were suggested to have a positive impact on crisis management effectiveness. Yet it was not demonstrated with advanced statistical tools if there is such a relationship. This study considers crisis management effort as a network effort and employs complex adaptive systems theory in order to understand factors influencing effectiveness of crisis management networks. Complex adaptive systems theory presents that more open communication lines in a given network or an organization would increase effectiveness of it since inner processes of the network or organization would obtain more information from the chaotic environment. Quality of informal relationships (casual relationships, social capital etc.) was hypothesized as a tool to open more communication lines within an agency which would eventually increase effectiveness of the network constructed by the organization. Based on the theoretical framework, adaptiveness capacity of the agencies was also tested in order to understand a correlation between adaptation and effectiveness of crisis management networks. Multiple case-study method was employed to identify incidents that can represent crisis management in full perspective. Terrorist attacks carried upon by the same terrorist network hit New York in 2001, Istanbul in 2003, Madrid in 2004, and London in 2005 were selected. First response phase of crisis management and policy changes after and before the attacks were discussed. Public administration processes and other social-economical conditions of countries were examined in terms of crisis management structure. Names of key agencies of selected crisis management systems were suggested by a social network analysis tool-UCINET. Six key agencies per incident were targeted for surveys. Surveys included a nine-item-quality of informal relationships, four-item-adaptiveness capability, and ten-item-perceived effectiveness of crisis management networks-scales. Respondents were asked to fill in online surveys where they could refer to their colleagues in the same incidents. 230 respondents were aimed and 246 survey responses were obtained as a result. Surveys formed a structural equation model representing 23 observed factors and 2 latent constructs. Confirmatory factor analysis was utilized to validate hypothesis-driven conceptual models. Quality of informal relationships was found to have a significant positive impact on perceived crisis management network effectiveness (Standardized regression coefficient = .39). Two of the adaptiveness variables, openness to change and intra-organizational training were also positively correlated with the dependent variable of the study (Standardized regression coefficient = .40 and .26 respectively). Turkish and American groups' differences suggested a social-economical difference in societies. Majority of the respondents were some type of managers which made it possible to generalize the results for all phases of crisis management. Discussions suggested improved informal relationships among crisis management employees to provide a better crisis management during an extreme event. Collaborative social events were offered to improve crisis management effectiveness. An agency's openness to change proposed that a crisis management organization should be flexible in rules and structure to gain more efficacy. The other adaptiveness variable, intra-organizational training efforts were proposed to have certain influence on effectiveness of crisis management network. Factors built latent construct of perceived crisis management effectiveness were also found out to be important on crisis management, which of some are ability to carry out generic crisis management functions, mobilize personnel and resources efficiently, process information adequately, blend emergent and established entities, provide appropriate reports for news media etc. Study contributed to the complex adaptive system theory since the fundamentals of the theory were tested with an advanced quantitative method. Non-linear relationships within a system were tested in order to reveal a correlation as the theory suggested, where the results were convincingly positive. Crisis management networks' effectiveness was demonstrated to be validated by a ten-item-scale successfully. Future research might utilize more disaster cases both natural and manmade, search for impact of different communication tools within a system, and look at the relationships among members of crisis management networks instead looking within an organization.