One goal among many in early childhood education and care (ECEC) is that children develop positive attitudes towards mathematics. In order to support this development, teachers need professional competence in both cognitive and affective-motivational facets. Teacher students need to develop this professional competence during their initial teacher education. This paper investigates how teacher students' age, mathematics self-efficacy (MSE), and mathematics anxiety (MA) affect their knowledge about mathematics and mathematics education in ECEC settings. A quantitative cross-sectional study with a paper-and-pencil questionnaire is used with a convenience sample from Norway. While MA affects students' knowledge as expected from previous studies, our findings show that MSE has a net suppressor effect on MA, revealing a reversal paradox. Higher MSE leads to lower MA which leads to better achievement in the exam that was used to measure students' knowledge. However, when MA is controlled, higher MSE causes lower achievement. Furthermore, we found that MA is affected by teacher students' age. Older teacher students and part-time students with experiences from working in ECEC institutions are less anxious about mathematics. This finding suggests that positive experiences with mathematics in daily life and pre-school situations can help students overcome their MA.