Professional Learning Communities (PLCs) are valuable spaces for collaboration and reflection to promote the transformation of teaching practice and resilience to change. In PLCs that are sustained over time, trust-building is a key element. In Latin America, school systems and educational models are based on mistrust, which in Chile is consistent with a highly unequal, individualistic, and competitive school system, making the generation of PLCs particularly complex. Through a longitudinal study, we describe how trust is built and maintained in a Chilean PLC of science teachers who meet regularly to share and reflect on their practice. We analysed 18 group sessions, six focus groups, and four interviews conducted over 11 years of this PLC. The results show relevant elements to initiate trust, such as building an initial bond of trust between some participants, recognising one's limitations, and negotiating common meanings and objectives. In the second stage, the free expression of experiences and emotions, reflecting on practice and validating its members' experiences allows for the construction of a genuine and highly valued space for professional development, which promotes practice transformation.