Background: Despite significant resources allocated to disaster preparedness and response capabilities nationally, preparedness and response for vulnerable and special needs populations is still largely lacking. Public health agencies could not possibly meet the disaster preparedness and response needs of all vulnerable and special needs populations especially in inner cities where populations are often quite diverse. As a result, increased attention has been given to innovative and unique approaches to strengthen community-based organizations' (CBOs) capacities as partners in emergency preparedness, response and recovery. Just as preparedness and response strategies play key roles in agencies responding to public health emergencies and natural disasters, CBOs must have enough capacity for disaster preparedness and response that allows them to continue operations before, during and after crises and disasters. Capacity for disaster preparedness and response is rarely within the scope of most struggling nonprofit organizations; however, the relationships they have formed to meet the needs of their vulnerable clients may contribute to this capacity. Purpose: This study explored the relationship between the number and types of interorganizational relationships that CBOs use to serve clients, their disaster preparedness and response capacities. How these relationships may be leveraged is also explored as part of the strategy of enhancing the overall level of an organizations capacity for preparedness and response. Methods: Mixed methods were employed to investigate the potential number and type of interorganizational relationships, organizational capacities and communication mechanisms associated with and influencing the disaster preparedness and response capacities of CBOs serving the homeless. The percent potential leverage, an organization's potential for using interorganizational relationships for disaster preparedness and response related activities, is determined for each organization. Findings: Factors that contributed to disaster preparedness and response capacity for CBOs serving the homeless included: types of organizations CBOs had relationships with, leadership at the organization, evidence of a culture of preparedness, working with/support from external organizations, a tendency of continual improvement and proximity of collaborators and resources. A summary of survey results is provided. Conclusions: In the struggle to incorporate disaster preparedness and response activities into the organizational structure and functioning of CBOs serving vulnerable populations, CBOs may find it useful to look at their interorganizational relationships more closely to determine which ones may also be used for disaster preparedness and response activities. The results of this study offer opportunities for public health to build relationships with CBOs serving vulnerable populations before, during and after crises and likewise for CBOs to tap into many of the services provided by public health to build relationships that are more meaningful.