An adequate understanding and classroom application of the Nature of Science (NOS) has become imperative for science teachers. Current research in senior high school science teachers' understanding of NOS is extensive but junior high school natural sciences teachers' understanding of NOS and planning of lessons requires further exploration. Six junior high school natural sciences teachers' understandings of NOS, and how they translated their NOS understandings into lesson planning in South Africa were explored. The conceptual framework of the NOS used in this research is drawn from the seven NOS aspects of explicit and implicit teaching of NOS. Data were collected from teachers' academic background questionnaires, Views of Nature of Science (VNOS(C)) questionnaires, semi-structured interviews and lesson planning documents of teachers. Data were analysed descriptively and interpretively. The findings revealed that junior high school teachers possessed inadequate understanding of NOS, and that their planning for teaching NOS was hardly influenced by their understanding of NOS aspects. The teachers' work-schedules and lesson plans showed little explicit links of NOS aspects to lesson content. The research findings have implications for the preparation of lessons with NOS aspects linked to the curriculum content.