The purpose of current research is to explore the influence of a science teaching method course incorporating explicit reflective NOS instruction on pre-service science teachers' views of NOS and justifications in their arguments related to their decision-making on socio-scientific issues. This study is a case study and the participants were 5 pre-service science teachers who were enrolled in elementary science teaching program. To track changes in participants' NOS views, the Views of Nature of Science Questionnaire was administered as preand post- test. To examine students' source of justifications, the decisionmaking questionnaire was administered as pre- and post-questionnaire. The research questions of the study were examined for each participant and presented to include the change in participants' NOS views, change in participants' source of justifications, and the relation between participants' views of NOS and their justifications in their arguments on SSI. The results of the study did not show a clear relationship between improved NOS views and the shifts in the sources of justifications used to make decisions on socio-scientific issues.