Pre-service language teachers develop their critical thinking in teacher education courses. They learn to teach critical thinking mainly during the teaching practicum. Their learning to teach CT takes place through different forms of mediation. Their learning is impeded by the gap between the curriculum goal and its implementation. Informed by a socio-cultural perspective, this study investigated how two student teachers developed their CT-oriented pedagogies in a pre-service language teacher education program in Hong Kong. Drawing on multiple sources of data including semi-structured interviews, relevant documents, and informal communication, the findings revealed the participants' growing pedagogical knowledge and competence in CT teaching, influenced by various forms of mediation – i.e., object-regulated, other-regulated, and self-regulated – afforded in the situated context. The gap between the curriculum's goal and its implementation was identified as a crucial factor that impeded their learning to teach CT in the program. The paper concludes with practical implications that can help integrate CT into pre-service teacher education programs with a view to preparing future teachers with a high level of CT and CT-focused pedagogies. Copyright © 2023 Elsevier.