Studies indicate that student teachers' engagement in continuous professional learning, (i.e., student teacher professional agency [STPA]), can improve their readiness for their careers. Unlike earlier qualitative studies often from the Global North, this research contributes geographical and methodological relevance to the literature by investigating STPA in a Brazilian teacher education program using a quantitative approach that aligns with an ecological understanding of STPA. A questionnaire assessing STPA, environmental (i.e., curriculum coherence and learning environment), and individual (i.e., teacher identity) factors was administered to 283 student teachers. Data were analyzed using structural equation modeling and network analysis. The student teachers' perceptions of (1) coherence between parts of the program, theory, and practice; (2) positive climate with their peers and mentors' recognition; and (3) teacher identity were the most relevant factors regulating STPA. These findings offer insights into developing a Brazilian teacher education curriculum to strengthen STPA.