The USAID Office of Inspector General (OIG) is initiating a review to identify lessons learned from our prior oversight of USAID’s third-party monitoring practices. Over the years, OIG has generated a significant body of work that has identified the beneficial role third-party monitors can play in tracking and verifying program data and results. We have also reported on shortcomings in administering third-party monitoring contracts and using this tool effectively to prevent fraud, waste, and abuse, including the diversion of U.S. foreign assistance to hostile entities. Distilling our findings and recommendations into key lessons learned will help inform the Department of State’s and other agencies’ efforts to administer U.S. foreign assistance. The objective of this review is to identify key lessons from our prior oversight of USAID’s third-party monitoring practices.