This study aimed to develop a measurement tool in order to assess preschool teachers' pedagogical content knowledge regarding mathematics. The study was based on 300 preschool teachers working in formal independent kindergartens and nursery classes of primary/secondary schools in the Kahramanmaras Province of Turkey. Among the participants, 150 were chosen for pre-application and 150 for the main application. The scale consists of five different case studies and a total of 35 items, including dialogues that focus on mathematical content and processes reflected in children's talk during their play. In calculating the reliability of the scale, Cronbach Alpha was found to be.95 for the pre-application and .96 for the main application. For the validity of the scale, exploratory and confirmatory factor analyses were performed. The exploratory factor analysis results revealed the scale to be a single-factor structure. When the factor loads of each relevant item were examined, no item was found to exist with a factor load value of less than .30. After confirmatory factor analysis was performed, the model fit indices of CFI, TLI, RMSEA, and SRMR values were found to be .91, .91, .06 and .06, respectively. These results show the model to be reliable to an acceptable level. Based on the findings, it could be concluded that the scale is an instrument that produces valid and reliable measures, and that it can be used in order to determine the preschool teachers' pedagogical content knowledge regarding mathematics.