Given the relationship between teacher beliefs and practices, it is critical to understand how pre-service teachers' past school experiences impact on their beliefs about teaching. There is a growing recognition of the influence of preservice teachers' prior mathematical experiences on their beliefs regarding mathematics instruction in the primary school classroom. This qualitative study aimed to investigate Hong Kong primary pre-service teachers' past experiences in learning mathematics and their beliefs about the teaching of mathematics. Nineteen primary pre-service teachers who had selected mathematics as their major in a teacher training program participated in the study. Each participant was required to complete three beliefs tasks in the individual interview in order to recall the teaching of their best mathematics teachers, articulate their memories of learning mathematics, and uncover the kind of primary mathematics teacher they planned to be. The results provided a valuable insight into the effects of pre-service teachers' prior mathematics class incidents on their espoused pedagogical beliefs. While both positive and negative learning experiences of mathematics had a positive impact on interviewees' beliefs about mathematics teaching, most demonstrated their willingness to learn from the past and realised the need to establish better learning environments for their future primary school students. Copyright © 2021 International Journal of Instruction.