Teacher professional development is a key factor in enhancing pedagogical interactions. However, implementing programs that are tailored to teachers' specific needs and teaching contexts remains challenging. This article examines a professional development program in pedagogical mediation based on action research, designed for early childhood educators in Chile. The study employed a case study design, involving nineteen teachers and six trainer educators. Data was collected through semi-structured interviews and written reports, which were analyzed using reflexive thematic analysis. The findings highlight four key aspects for teacher professional development: reflective chaining, video-based training, the role of the critical friend, and work within professional learning communities. These categories form a continuous action-research and reflection spiral that enhances teaching professionalism and self-awareness of practice, promoting a shift from the individual to the collective and from the simple to the complex. This approach fosters a collaborative culture of improvement, strengthening professional development and serving as a model for other programs that contribute to quality in this educational level.