In schools, classroom talk is often dominated by teachers´ lecturing or asking closed questions followed by teachers’ evaluative feedback. When the teacher presents ideas to students or uses the question-response feedback, the talk is considered as authoritative talk. On the other side, during dialogic talk, the teacher reacts to students´ views and responses. The important role of the teachers in promoting dialogic classroom talk has been demonstrated in many previous studies. However, little is known about how student teachers use different talk forms, especially in inquiry-based biology lessons which is the focus of this research. The primary school student teachers’ lessons – a total of 14 lessons of five student teachers – were videotaped and audiotaped. The data were analysed using theory-based content analysis. The results show that the primary school student teachers used more authoritative classroom talk than dialogical classroom talk in their inquiry-based lessons. Mainly, non-interactive authoritative talk form was used by all student teachers, and interactive dialogic talk form was used least. Authoritative talk was used in all stages of the inquiry-based lesson. Dialogic talk was used more during introduction and examination stages. The findings suggest that in teacher education, student teachers need scaffold in talking with pupils when carrying out inquiry-based teaching.