The theory-practice debate has been a perennial issue in initial teacher education (ITE). By reporting a mixed-methods study in an ITE programme characterized by a university-based 'theory-first' approach in Hong Kong, this study offers useful empirical evidence to analyse the theory-practice issue. 346 student teachers of a BEd Programme participated in the quantitative survey, 15 of whom were interviewed. The quantitative findings showed significant positive correlations between three types of perceived professional competence and two aspects of student teachers' engagement with the theory-practice link. The qualitative findings offered an in-depth understanding of the ways in which student teachers connected theoretical knowledge learned in ITE coursework and practical experience in ITE fieldwork in developing their professional competence: (1) theoretical knowledge as a guide for professional decisions and a tool for reflection on practice; (2) practicalizing theoretical knowledge: adapting theoretical knowledge to practice situations. In the process of engagement, theoretical knowledge was transformed and adapted to practice situations when student teachers coped with the challenges of the teaching contexts in their ITE fieldwork. While affirming the value of student teachers' engagement with the theory-practice link, the findings of the study shed light on ITE practices for preparing student teachers for such engagement.