The purpose of this study was to use a Constructivist Grounded Theory methodology to understand the learning experiences of trainers who completed a professional development trainer certification. Specifically, this study explored how trainers described their learning experiences, the catalysts trainers identified as instrumental to their learning, and the nature of developmental relationships in the learning process. By uncovering an understanding of these learning experiences, the study provides valuable insights into improving professional development programs' effectiveness and the nature of the developmental relationships that support learning experiences. Ten trainers were interviewed using a semi-structured interview guide. Data analysis suggested that the factors that most strongly influenced learning and transformation include the evolving learner identity, the formal structure and resources of the certification process, learner engagement, developmental relationships, peer learning, identification of transformation, and the nurture of a lifelong learner mindset. Using these factors, a theoretical framework, Professional Development Components for Learning and Transformation, was developed to design transformative trainer certification processes. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]