This qualitative case study explores how a group of pre-service teachers develop teacher competence through conducting their own classroom-based research during teaching practicum. By conceptualising teacher competence as knowledge, strategies, and dispositions, this study used semi-structured interviews with the participants and their final-year dissertations. The findings revealed that the classroom-based research helped the participants gain competence in research and in teaching, as they gradually developed and practicalised research knowledge in classrooms, acquired social strategies in schools, and cultivated dispositions as classroom-based researchers. The paper concludes with practical implications on supporting pre-service teachers’ research-teaching integration and developing their sense of self-efficacy as a classroom-based researcher to benefit their future practice.