Many learners hold traditional beliefs about mathematics that can hamper their learning in the discipline. To address this issue, a "history-based" intervention program entailing problem-solving and writing activities that instigate cognitive conflict was implemented. Data sources were pretest and posttest scores of a 12-theme questionnaire designed for this study called "Prospective teachers' beliefs questionnaire about mathematics learning" and written reflections of prospective teachers. The survey of the prospective teachers beliefs related to the nature of mathematics and the way it is learned, taught, and practiced showed a great majority of them failed to hold progressive beliefs. Fortunately, the intervention program has helped the prospective teachers revise and correct their beliefs, thoughts, and understandings. Study of the prospective teachers' written reflections and observations of their oral presentations during whole-class discussions strengthen the results of the quantitative study.