The purpose of this study was to examine the reliability and validity of the Turkish adapted version of Mathematical Development Beliefs Scale developed by Platas (2015). The scale can also be used to determine preschool teachers' beliefs about Mathematics education. After obtaining the permission from the developer of the questionnaire, the items of the questionnaire were run through a double-translation process where they were first translated into Turkish and then, retranslated into English. Then, the scale was sent to an expert in the field and the necessary corrections were made. The research was carried out with 203 preschool teachers working at kindergartens in state schools of the Ministry of National Education (MEB) and at kindergartens in private schools in Ankara. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were applied to the collected data. Based on these analyses, it was found that the adapted scale into Turkish consisted of 40 items, which were and gathered under four factors. The Cronbach alpha coefficient for the overall scale was .86. Test-retest correlation coefficient was found as r= .87. These values indicate that the questionnaire is highly reliable. The scale is found to be valid and reliable and appropriate to use in Turkish culture.