The purpose of this study was to investigate the 9th-grade students' understandings of the nature of scientific knowledge. The study also aimed to investigate the differences in students' understanding of the nature of scientific knowledge by gender, and school types. A total of 575 ninth grade students from four different school types (General High, Anatolian High, Vocational High and Super Lycee) participated in the study. Data were collected utilizing an adapted version of the Nature of Scientific Knowledge (NSKS). Data were analyzed by using MANOVA. Results revealed statistically significant differences in the student's perceptions of nature of scientific knowledge by gender and school types. It was also found that many of the participants had inadequate understanding of nature of scientific knowledge. (Contains 1 figure and 3 tables.)