This article aims to identify the professional competencies that primary school teachers in Vietnam need for effective mathematics teaching and the extent to which teacher-training colleges prepare pre-service teachers with those competencies. A mixed method approach with an explanatory sequential design was employed. Questionnaires were sent to 493 pre-service teachers and interviews were conducted with 20 teacher trainers from five major teacher-training colleges in Vietnam. The findings indicated that Vietnamese pre-service teachers were adequately trained in terms of mathematical content knowledge yet were less ready in terms of mathematical teaching pedagogies. Mathematical pedagogical content knowledge was reportedly an often-neglected area at teacher-training colleges and was subsumed under general pedagogical content knowledge. The study has both theoretical and practical contributions to the development of professional qualities for primary school teachers teaching mathematics at primary school in Vietnam.