Over the past 2 decades the study of students’ (and teachers’) mathematics-related beliefs has gradually received more and more attention from researchers in the field of educational psychology as well as from scholars in the area of mathematics education. In this article positive beliefs about mathematics and mathematics learning are considered as a major component of competence in mathematics. Results of empirical studies are presented showing that primary school students often have negative and/or naive beliefs about mathematics learning, focused on the phenomenon of “suspension of sense-making” in mathematical problem solving. A design experiment is then described in which a learning environment was developed and implemented, which was intended to improve students’ performance in problem solving as well as their mathematics-related beliefs. This and related work support the hypothesis that changes in the classroom culture and practices can foster students’ mathematical thinking and learning as well as their beliefs, but they do not provide a more in-depth understanding of how the interaction processes and patterns in the classroom influence students’ math learning in general and their mathematics-related beliefs in particular. Using a socioconstructivist perspective as a theoretical framework, the article then discusses a recent investigation that precisely attempts to contribute to unraveling the reciprocal relationship and impact between students’ beliefs, on the one hand, and crucial components of the learning environment, especially teachers’ beliefs and the classroom culture, on the other hand. The article concludes with some critical reflections and suggestions for future inquiry.