Purpose: The purpose of this study was to explore the conditions and challenges that facilitate teacher professional learning through the implementation of pedagogical mentoring (PM) within the Chilean school context. Design/methodology/approach: This study employed a qualitative methods approach, utilizing an instrumental case study. As the primary data source, researchers conducted 14 individual, semistructured interviews. Participants included two co-mentors, six mentor teachers and six mentee teachers from two K-8 focal school sites. Data were examined using the content analysis method. Findings: Results revealed five aspects that contributed to PM's execution--the voluntary participation model, the reflective emphasis, the focus on teaching and learning, the facilitating role of the principal and co-mentor support. At the same time, the findings indicated three factors that hindered PM's success: interruptions due to schedule conflicts, limited dissemination throughout the school community and assimilation of the values embedded in the Chilean teacher evaluation system. Practical implications: PM holds great potential for collaborative professional development and continuous improvement of teachers' instructional practices, drawing on their experiences and resources and leading to the strengthening sense of professionalism in teaching and in teachers' social esteem. Originality/value: This is the first research to address a formal PM project in Chile aimed specifically at in-service teachers. Previous projects in the country have focused on novice teachers. Unlike other initiatives in the region, this project does not focus on teacher induction but on capacity building within schools through collaborative work. This research also adopts an approach based on support for teachers' professional development, while in Chile the main policies currently focus on teacher evaluation.