The purpose of this study was to examine teachers' experiences implementing the Social Emotional Learning (SEL) program RULER. In recent years, schools have adopted SEL programs to improve the skills of self and social awareness, emotion regulation, responsible decision-making, problem-solving, and relationship management of students. SEL programs have been examined for their effectiveness in improving school climate and emotionally supportive school culture. Additional studies are needed that focus on the successes and challenges teachers experience when implementing the program to provide a sustainable implementation plan for schools. Using the basic qualitative research design, teachers' experiences implementing the RULER program were explored through semi-structured interviews. The theoretical framework was the Self Determination Theory. Twelve teachers participated in the study representing four different schools. All participants were trained in the RULER approach and had experience implementing it in their respective schools. The collected data were analyzed using open, axial coding. The findings in this study revealed three major themes: preparation and planning, implementation challenges, and implementation successes. The subthemes included staff training, professional development, pacing, buy-in, time, prior SEL background, and administration support. Future studies should apply triangulation and include a larger population and various stakeholders involved in implementing the RULER program. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]