Many K-12 students today have not developed the skills they need for success in the "Globalization 3.0" era in terms of mastery of foreign languages, cultural awareness, proficiency in world geography, and knowledge of current global events, as well as "soft skills" like problem-solving, critical thinking, empathy, and effectively communicating with others who may not share their points of view. In addition to the new global competition faced by our students, the rapid advances in technology have given them access to a wealth of information that they will need to know how to access, filter, and interpret to solve problems that did not exist in previous generations (Friedman, 2005). The purpose of this mixed-methods study was to examine how a series of professional development (PD) sessions on global citizenship education (GCE) impacts teachers of Grades 3-5. Specifically, the study analyzed the extent to which this training increased teachers' knowledge of GCE and competencies, and their perception of their own ability to integrate the four global competencies as defined by Asia Society Center for Global Education (2011). These competencies include investigating the world, recognizing perspectives, communicating ideas, and taking action. This study can add new knowledge to the field of GCE. Currently, there is very little research on how PD impacts teachers' ability to provide GCE opportunities to students. Numerous organizations call for GCE to be taught within all subject areas to prepare students for today's global society (Asia Society & OECE, 2018). Unfortunately, the United States is behind many other developed countries in this endeavor (Global Education Network Europe [GENE], 2018). In order for American students to become globally competent, educators must be equipped to implement GCE in their classrooms.