A mixed-methods design was used to assess the current capacity of human service agencies to provide services in a major disaster, identify challenges and successful strategies for providing those services, and formulate specific recommendations for government planners and the nonprofit sector to promote the integration of human service agencies into emergency preparedness and response. A web-based survey was completed by 188 unique human service agencies, 31 semistructured interviews were conducted with human service agency and government leaders from southeastern Pennsylvania and the mid-Atlantic region, and a collaborative planning meeting was held to review the findings and develop systems-based recommendations. Survey results indicated that human service agencies serve the most vulnerable communities during disasters and would welcome integration into preparedness and response plans, but they currently face challenges that include a lack of real-time communication and opportunities for collaborative planning with government partners. Interview findings were grouped according to 5 themes that emerged: capacity, coordination, communication, training, and leadership. This study identified recommendations to assist human service agencies, local health departments, and emergency management agencies as they work to ensure that needed human services are available during disasters, despite the resource challenges that most agencies face.