The study investigated Finnish in-service primary school teachers' (N = 815) sense of professional agency and inadequacy in teacher-student interaction over a five-year period. Teachers' professional agency refers to a capacity that prepares for new learning, and consists of teachers' motivation, self-efficacy beliefs, and strategies for learning. Analyses were conducted using structural equation modelling and the cross-lagged panel model. The results showed that Finnish primary school teachers experience strong and stable professional agency, as well as moderate and stable levels of inadequacy over time. In particular, teachers' efforts to build collaborative learning environments and revise pedagogical practices can reduce the sense of inadequacy in teacher-student interaction.