Teacher competence is a multi-dimensional construct that includes beliefs as well as knowledge. The present study investigated the structure of prospective preschool teachers' mathematics-related beliefs and their relation to content knowledge and pedagogical content knowledge. In addition, prospective preschool teachers' perception and planning skills were assessed as indicators of teacher performance. Questionnaires were used to measure beliefs, paper-and-pencil based achievement tests to measure knowledge, and a video-based test to measure perception and planning abilities. Confirmatory factor analyses revealed that prospective preschool teachers' mathematics-related beliefs can be distinguished into a static, a process, and an application orientation. Structural equation modeling revealed that an application orientation and mathematics pedagogical content knowledge can predict the ability to perceive mathematical learning situations and to plan adequate actions. Conclusions for preschool teacher education are drawn from the results.