The integration of science, technology, engineering, and mathematics (STEM) education, also referred to as integrative STEM education, is a relatively new interdisciplinary teaching technique that incorporates an engineering design-based learning approach with mathematics, science, technology, and engineering education (Sanders, 2010, 2012, 2013; Wells, 2010, 2013). Over the past 11 years, 475 teachers and administrators, representing kindergarten through eighth grade teachers and elementary school administrators from 7 school districts in South Carolina, have participated in an Integrative STEM Education Institute. In this Institute, participants developed knowledge and skills to create and implement integrative STEM education activities for use in their classrooms. Participants learned how to incorporate problem-based and project-based learning that helps students work in groups to develop cross-curriculum skills. The purpose of this article was to evaluate the immediate and long-term effectiveness of the Institute. Quantitative survey data from pre-post surveys immediately revealed a statistically significant increase in self-efficacy regarding the Institute's learning objectives. In addition, a survey was sent to alumni from the 2012-2015 Institutes. The results from this survey revealed that a significant number of alumni felt empowered through the Institute to implement integrative STEM education in their classrooms and build sustainable integrative STEM education programs at their schools following attendance at the Institute.