Effective management of marine protected area (MPAs) requires continuous feedback of information to achieve objectives. In 2000, a collaborative initiative was launched to improve the management of MPAs. The initiative focused on working with managers, planners, and other decision-makers to develop a set of indicators for assessing the effectiveness of MPA use. This initiative was aimed at both enhancing the potential and capability for adaptive management of MPAs, as well as improving our understanding of how effective MPAs that are now being used around the world. This paper presents an overview of the MPA management effectiveness methodology and indicators, summary results of the testing phase of the guidebook at 18 MPAs around the world, and considerations for its application and use as an adaptive management tool for MPAs.