This study aimed to explore pre-service chemistry teachers' beliefs about constructivism and the influence of their beliefs in their teaching practice. For this purpose, semi-structured interviews were carried out with eight pre-service teachers in order to understand their belief structures. Pre-service teachers' beliefs about constructivism were classified in three categories which are weak, moderate, and strong conceptions of constructivism. For detailed exploration, three cases of pre-service teachers representing these three categories were selected. The findings of this study showed that most preservice teachers in this study did not have a strong conception of constructivism and the relationship between the pre-service teachers' beliefs and their practice was not clear-cut.