Traditionally, in many countries there exist different teacher education programs for special education and for regular or inclusive education, not at all with similar underlying paradigms for teaching and learning or similar definitions and understanding of the term inclusion. In this context, one central question is how to define inclusive mathematics education, how to address the manifold aspects, and how to reduce discrimination and marginalization. On the one hand, teacher education programs might focus on diverse groups and specific students, like students with special needs and integrate important questions of special education. On the other hand, teacher education programs might take explicitly a broader perspective, considering the mathematical learning of all students and not taking a specific focus. In this contribution we present research results of the project "ProViel" ('professionalisation for diversity') to discuss how a teacher education program can be designed to address both with the underlying paradigm of making mathematics accessible for all students, and what role pre-service teachers' beliefs as well as their self-efficacy might play. The project aimed at subject-specific concept development and research concerning teacher education for inclusive mathematics on the primary level, considering different points in time within the whole education program. Quantitative data of pre-service teachers' beliefs and self-efficacy have been analysed, while they participated in different university courses and a practical phase at school. Key findings of this study are, that pre-service teachers' beliefs about student achievement and their self-efficacy for inclusive mathematics teaching changed during the teacher education program.