There is worldwide agreement that the understanding of the Nature of Science (NOS) is a critical component of scientific literacy. However, evidence indicates that both pre-service and in-service science teachers hold naïve views about NOS. Even so, the characteristics of pre-service teachers that influence their learning of NOS are not fully described. In this context, the goal of this study is to connect the understanding of NOS of pre-service teachers with a different disciplinary training (second year of biology education programme versus first year of elementary-education programme). The research is quantitative with a quasi-experimental design. To assess the understanding of NOS in students' science teachers, an adapted version of the VNOS-D + instrument was applied before and after the intervention. Both groups received three NOS teaching sessions using History of Science as context and implementing an explicit and reflective instructional strategy, centered on students. The main results of this study indicate that both groups significantly improved their understanding of NOS, and in the same magnitude, after the intervention. In addition, the understanding of some of the aspects of NOS improved more easily than others. Finally, there is a discussion about the contribution of this study to the pre-service science teacher's education.