The purpose of the present study was to understand the nature of the link between science teachers' epistemologies and their socioscientific issue (SSI) teaching discourse. It is important to consider this link due to the limitations of science teachers in shifting from monologic to more dialogic orientations in their teaching, despite SSI-based science education reforms in many countries. Teachers' epistemologies are likely to contribute to the difficulties experienced in this shift. We selected three science teachers using purposive sampling procedures. Using classroom observations and follow-up constructivism-oriented interviews, we selected one non-constructivist, one moderately constructivist, and one constructivist science teacher. We then examined these teachers' (knowledge-based and science-based) epistemologies by two semi-structured interviews. The teachers taught one SSI topic and then we conducted classroom observations. Benefiting from highly used classifications, we classified teachers' epistemologies and discourses in the transcripts. The results showed that there were some coherences and incoherences between science teachers' epistemologies and their SSI teaching.