Accountable care organizations (ACOs) are a new health care reform initiative that has been highlighted as one of the most important organizational structures that could lead to quality improvements and cost savings in the United States through shared savings. The inability of health care managers to successfully implement ACOs could result in financial losses, reduced patient access to health care, and poor patient outcomes. Grounded by von Bertanlaffy's general systems theory, the purpose of this multiple case study was to explore the system change strategies health care managers used to implement an ACO to meet ACO quality and cost standards. Health care managers from Arizona, New York, and Wisconsin who successfully implemented ACO system change strategies in their organizations comprised the population for this study. Data were collected through face-to-face semistructured interviews with 9 health care managers. Data were analyzed using methodological triangulation, thematic analysis, and Yin's 5 analytic techniques to identify patterns and themes. Three main themes resulted from the data analysis and included leaders with system change strategies improved successful ACO implementation, leaders who implemented health information technology improved successful ACO implementation, and leaders with care management system change strategies improved successful ACO implementation. The application of the findings from this study may contribute to positive social change because health care managers may use these system change strategies to successfully implement ACOs to improve patient care and access and reduce the financial burden of health care costs throughout the United States.