Improving understanding of nature of science and scientific knowledge for individuals has been seen one of the essential objectives for science education for years. Teachers have a critical role in the process of learning nature of science by students. For this reason, we have turned our attentions toward improving science teachers‟ views about nature of science and scientific knowledge. This study focused specifically on introducing the explicit-reflective inquiry-based professional development workshop designed by the researchers. Second aim of this study is to examine the impact of explicit-reflective inquiry-based professional development workshop on preservice chemistry teachers‟ understandings of nature of scientific knowledge. Participants of this study were 20 preservice chemistry teachers at Gazi University. In order to exposing the changes in understandings of nature of scientific knowledge, Turkish version of The Nature of Scientific Knowledge Scale (NSKS) and interviews were used in a pre/post format. The result of the Paired Samples T-Test, used to investigate the effect on the understandings about scientific knowledge, indicated that understandings of preservice chemistry teachers had a significant progress. The quantitative analysis of the scores which the participants got from each of six categories in NSKS were put forward significant differences in term of only creative and developmental categories. Also, in the qualitative analysis of the transcripts of interviews came out similar results. It seems that our explicit inquiry-based professional development workshop moved participants towards more adequate understandings about nature of scientific knowledge.