This research aimed to identify the educational approaches that pre-service elementary mathematics teachers adopt for their first teaching practice (TP) and the reasons for their choices. It was carried out with thirteen pre-service teachers (PTs). These PTs were observed during their first TP in a real school setting, and interviews were conducted after the TP. Our observations led us to the conclusion that PTs generally tended to utilize traditional teaching approaches. The interviews revealed that PTs' epistemological beliefs and beliefs about learning and teaching mathematics are largely in line with constructivist theory, and that their tendency for traditional approaches was due to: the influence of past educational experiences, the teaching styles of in-service teachers working at practice schools and their negative opinions about constructivist approaches, the limitations of their university educations, their lack of experience, and choosing the easier option. We conclude with a discussion of the implications of these findings for teacher training in mathematics.