The study aimed to investigate the effect of project supervision training offered to Biology teachers on their views of the nature of scientific inquiry. We employed an action research design, as one of the qualitative research methods in this study. The participants were composed of 39 Biology teachers who had attended training on project supervision. The data were collected using Views of Scientific Inquiry (VOSI) instrument developed by Schwarts, Lederman, and Lederman (2008). Following that, and a semi-structured interview form developed by the researchers was conducted. The data were analyzed using content analysis methods through creating codes and themes. The results revealed that the project supervision training supported development of teachers on five dimensions; scientific research is directed by questions, use of different methods in scientific investigations, research has many purposes, justification of scientific knowledge, and differences between scientific data and evidence. It was also found out that the training had positive effects on their professional practices.