Inquiry-based learning has generally accepted by scholars as a most effective teaching approach in biology education. The talk during inquiry-based teaching needs to be practiced. There is less evidence how student teachers talk with students during their inquiry-based biology instruction. This knowledge is needed in supporting student teachers to develop their teachership in biology education. In this qualitative case study, the dialogic talk of biology student teachers (N = 6) was studied in the context of inquiry-based lessons in lower secondary school. The student teachers' lessons were video and audio recorded and the data was analyzed using content analysis. The student teachers used dialogic talk in their inquiry-based instruction only occasionally, mainly in the examination and the conclusion stages. During the introduction stage, dialogic talk was less used and it was mainly explaining and instructing the content. In the examination stage, student teachers also guided students and stated facts. During the conclusion stage, student teachers mainly explained and also evaluated students' statements. The lesson's topics and methods used in inquiry-based learning may enable the dialogic talk of student teacher to some extent. However, teacher education should focus more on scaffolding student teachers' talk with their students in all kinds of inquiry approaches.