Nature of Science (NOS) understanding is recognized as one of the important components of scientific literacy. Teachers have an important role in raising scientifically literate individuals. For this, it is suggested that teachers should be continuously supported in terms of their understanding of NOS and teaching approaches. In-service education is one of the ways to support teachers. This education can enable teachers to gain knowledge and skills related to NOS content knowledge and learning approaches. In this study, the effects of an in-service education to provide teachers with the knowledge and skills related to their understanding of NOS and the teaching strategies and methods they need were investigated. The in-service education lasted 20 hours with the participation of 27 chemistry teachers. Family Resemblance Approach Scale was used as pre-test and post-test to evaluate the effects of the training. Statistics tests were used in line with the data obtained from the scale. In this context, scale sub-dimensions were analyzed, and independent sample t-test and Mann-Whitney U test were applied. As a result of the findings, it was determined that in-service education had a significant effect on teachers' understanding in the scientific knowledge dimension of the scale.