Science teachers' epistemological beliefs about scientific knowledge have significant implications for their classroom practices and ultimately for the students' learning of science. The main purpose of this study was to investigate a science teacher's conceptions and understanding of the nature of science (NOS). As teachers' conceptions about NOS are embedded in their experiences of learning and teaching science, I used the life history approach for this study. The study was conducted on a single science teacher, Ikraam (a pseudonym), a young male teacher working in a community-based co-education school in one of the socio-economically disadvantaged areas in Karachi. His life story plays a vital role in this study to illustrate his views of NOS. However, I have also narrated my own story to exemplify my own perspective as a researcher. The data includes six life history interviews with Ikraam, two group interviews with fourteen students in two groups, eight classroom observations with post-lesson discussions, documentary analysis, and a number of informal conversations with Ikraam, his colleagues and students. The study indicates that in some cases, the participant teacher holds informed conceptions about the nature of science. However, in a few important areas he showed naive views. For example, he ascribed to a naive hierarchical view of the relationship between theories and laws whereby theories become laws if evidences support them. Similarly, while he was aware that children are not empty-vessels, he seemed to be unaware about the theorydependent nature of observation. Many of his existing conceptions of NOS have also been influenced by some of the teaching in the Advanced Diploma in Education: Science programme he was undertaking at the Aga Khan University Institute for Educational Development (AKU-IED). The study also revealed that the teacher's conceptions of the nature of science are embedded in his experiences of learning and learning to teach. He is more likely to teach or not to teach the way he has been taught in school, college or in professional development programmes according to his espoused theories. The analysis of the findings of the study further suggests that NOS may be explicitly included and defined in the National Curriculum for Science and teacher education programmes, and translated into textbooks, instructional and assessment practices.