Economic development and environmental sustainability were often not associated together in the World Bank’s activities prior to the 1990s. Since then, major reforms have been implemented and the World Bank has mainstreamed the environment into all of its activities. A major part of these reforms included collaborating with the Global Environment Facility (GEF) to implement projects with few risks and many positive environmental returns. This thesis attempted to assess the impact of the GEF on the World Bank’s environmental reform. This study uses 252 World Bank-GEF projects, and 1181 World Bank projects (without a GEF component) from 1991- 2010 to measure direct, indirect, and cumulative impacts using project outcome ratings as the response variable. This thesis finds that increased competition among GEF agencies for limited GEF funds and higher financial commitments result in better project outcomes ratings with positive direct and cumulative impacts respectively. This research concludes that a competitive model rather collaborative model should be adopted when multiple agencies partner with a common intermediary as it will encourage increased spending on the environmental aspects of projects.