Aim: This paper reports a mixed methods study on the contribution of various aspects of professional learning in initial teacher education (ITE) to student teachers’ perceived professional competence in a Five-year Bachelor of Education Programme in Hong Kong. Special attention is paid to student teachers’ non-formal learning in higher education. Content: The mixed methods study was conducted in the context of university-based ITE programme in Hong Kong. A total of 282 student teachers participated in the quantitative survey, 18 of whom were interviewed. Exploratory and confirmatory factor analyses revealed four aspects for professional learning in ITE, and three factors for professional competence. The four aspects of professional learning in ITE are, in order of subjective importance to student teachers, Learning in ITE Fieldwork, Pedagogy-related Learning Experience, Previous Experience in School and Work, and Undergraduate Learning Experience: Formal Learning and Non-formal Learning (hereafter, Undergraduate Learning Experience). The results of multiple regression analyses indicated that student teachers’ Undergraduate Learning Experience is a significant predictor of all the three factors of professional competence, namely Competence in Classroom Teaching, Pedagogical and Educational Knowledge, and Competence to Work in Schools: Working with Others and Understanding School-wide Matters. Among various aspects (formal and non-formal learning) of undergraduate learning experience, this paper pays special attention to non-formal learning. The qualitative findings show that student teachers’ repertoire of teacher knowledge expanded in non-formal learning opportunities afforded by service learning, co-curricular activities and student exchange programmes. They constructed pedagogical content knowledge (PCK), general pedagogical knowledge (GPK) and knowledge of context, mainly through their own hands-on experiences, professional dialogue with practitioners