Concerns about the negative mathematical beliefs of prospective primary teachers have arisen from evidence that such beliefs detrimentally impact future teaching practices. The aim of this study was to explore factors contributing to the effectiveness of a mathematics content-focused intervention designed to nurture positive mathematical beliefs. Utilising interviews, concept mapping, workshop observations and document analysis, shifts in the mathematical beliefs of prospective primary teachers were revealed. The role of the mathematics education tutors was critical in contributing to the development of positive beliefs. In particular, their abilities to develop a positive rapport with prospective teachers and to create learning environments conducive to increased understanding of mathematics concepts were most influential. Implications for primary mathematics teacher education courses are addressed.