This one-year phenomenological study focuses on exploring sources of teacher self-efficacy (TSE) among pre-service secondary mathematics teachers during their initial teacher education. The findings of the study shed light on the significance of enactive, social and affective sources of TSE, and suggest the need to broaden the understanding of these sources. They also emphasize the need to explore previously unexamined aspects of TSE, in order to gain a more comprehensive understanding of this important construct in the field of education. Furthermore, the study highlights the importance of considering factors beyond just mathematics teacher knowledge when considering mathematics teacher professional learning.