The Professional Learning Community (PLC) model has moved to the forefront in the field of education as one of the most effective frameworks to improve student achievement and overall school success. The research conducted for this paper provides evidence for systemic and action based improvement using the PLC model in four diverse venues: candidates enrolled in a leadership preparation program, a school faculty to improve its learning culture, a district level team, and a business partnership. The first case study used the PLC framework to develop, implement, and assess the preparation and training of educational leadership candidates. The second case study was incorporated by a principal and faculty to identify ways the PLC model could be put into practice to enhance learning in the school culture. The third case study was the use of the PLC model with a superintendent and a team of school principals. Finally, the PLC model was introduced to develop a business partnership. The business partnership was a unique use of the PLC model, which has historically been utilized in the educational arena. Two fundamental concepts, andragogy and the knowing-doing gap, were applied to each case study. The application of andragogy (Knowles, 1984), the theory of adult learning, attempts to explain why adults learn differently than other types of learners. Andragogy suggests that the best practices in adult learning provide learners with principles of high levels of involvement in planning, experiential learning, relevance, and pragmatic application (Knowles, 1984). The second premise applied to this PLC study was the knowing-doing gap suggested by Pfeffer and Sutton (2000). This concept has historical roots in many areas including education, whereby adults are knowledgeable within an area of learning but frequently fail to take action. Participants in each case first gained knowledge of the PLC model, followed by efforts to apply the main principles of the model in order to impact their role and environment. The emphasis on theory to practice is supported by the adult learning literature as well the PLC literature in "Learning by doing: A handbook for professional learning communities at work" (Dufour, Dufour, Eaker, and Many, 2006). The four cases were developed by first introducing the principles of professional learning communities followed by opportunities to apply it to themselves and others in a school or business environment.