The purpose of this study is to develop the Inclusion Knowledge Test (IKT) for assessing preschool teachers' knowledge of inclusive practices and to examine its psychometric characteristics. To achieve this purpose, the researchers wrote short stories (vignettes) focusing on the various aspects of inclusive practices, such as assessing the development of children with disabilities, adapting a preschool curriculum, and interacting with families of children with disabilities. Having been evaluated by a panel group consisting of experts who worked in special education fields, all vignettes were reviewed, and necessary adjustment and changes were made. Then the data were collected from the IKT responses of 169 preschool teachers, and validity and reliability studies were carried out. According to the results of the analysis, the IKT consists of 24 items (vignettes) loaded on one factor, and the factor loads of all items were more than .40. Cronbach's Alpha is .917. The findings showed that the preschool teachers have very limited knowledge of inclusive practices, and their IKT scores did not change according to their experience or whether or not they had children with disabilities in their classroom. However, there was a significant difference between the IKT scores of the teachers who had and did not have a special education course during their pre-service training.