The nature of science (NOS) has become a central goal of science education in many countries. This study sought an understanding of the extent to which a nature of science course (NOSC), designed according to the conceptualization of pedagogical content knowledge (PCK) for teaching nature of science (NOS), affects in-service science teachers' understanding and learning of NOS, and their orientations towards teaching it. A qualitative research approach was employed as a research methodology, drawing upon pre- and post-instruction NOS questionnaires, field notes, and in-service teachers' weekly journal entries and assignments. Open-ended NOS questionnaires, used to assess participants' understandings of NOS, were analysed and categorized as either informed, partially informed and naive. Other qualitative data were analysed through an inductive process to identify ways in-service teachers engaged and learned in the NOSC. The results indicate that at the beginning of the course, a majority of the in-service science teachers held naive understandings of NOS, particularly with respect to the definition of science, scientific inquiry, and differences between laws and theories. They viewed implicit project-based science and science process skills as goals of NOS instruction. By engaging in the course, the in-service science teachers developed an understanding of NOS and orientations to teaching NOS based on various elements, especially reflective and explicit instruction, role modelling, and content- and non-content embedded instruction. The aim of this study is to help science teacher educators, consider how to support and develop science teachers' understandings of NOS while being mindful of PCK for NOS, and develop methods for teaching NOS frameworks.