In a mixed methods design, this study examines prospective teachers' beliefs on co-teaching of general teachers and special education teachers. The quantitative approach comprises the development of a questionnaire regarding beliefs on teachers' roles and benefits of co-teaching in inclusive classes. The model fit and group mean differences of the final sample (n = 510) are reported. In a qualitative approach, focus groups with 56 participants were conducted and analyzed with the grounded theory method to provide further insights into prospective teachers' beliefs. The emerged core categories, role clarification, role reference system, and roles at eye level, disclose a multidimensional understanding of prospective teachers' beliefs on co-teaching.