While initial teacher education (ITE) has been acknowledged as an important process for improving the quality of education by preparing future teachers, less attention has been paid to the support of the continuous professional learning of teacher educators (TEs). This study reports on the supporting processes and tools for a collaborative inquiry-based systematic reflection of five TEs and the effects of their use in constructing professional knowledge about ITE. The reflective written reports and reflective discussions of the TEs are thematically analysed to show the focus of inquiry, the links among inquiry, reflection, and action, as well as the contributing role of collaboration within a professional learning community (PLC). The results show that the TE inquiry was a continuous process of exploring the beliefs, understandings, and participation of pre-service teachers (PSTs) during teaching; the impact of the teaching context on TE actions and decisions; and the ways in which their collaboration enhanced professional learning. The inquiry results informed the reflections and practice design of TEs. Guiding questions, sustained interactions among the PLC members, and support from a facilitator created opportunities for the collaborative construction of the professional learning of TEs. This article provides TEs or/and facilitators of PLCs in teacher education with a methodology for supporting professional knowledge through collaborative inquiry and reflection.