This article focuses on student teachers' professional development and explores how the students connect theory and practice in these processes. Data consist of 17 talks during weekly seminars with 15 preschool student teachers and a group of researchers both at campus and at the practicum placements during their first term. Initially, the researchers introduced discussions with an aim to challenge the students' views on general societal issues as well as specific issues related to the preschool practice. Eventually, the seminars changed toward student and researchers being more equal interlocutors. Experiences were discussed and relations between theory and practice were elaborated. Analyses from an ecological perspective of teacher agency show that the student teachers' agency develops from a naïve to a proactive understanding of the profession. The early practicum period in combination with regular seminars was important for the student teachers' developing profession. The practicum period provides practical challenges, and the seminar discussions with researchers provides theoretical challenges. Implications for teacher education are discussed, such as offering horizontal teacher networks where students get support to be able to develop their professional agency.