In this study, it was aimed to carry out the validity and reliability study of Number Sense Screener (NSS)'s Turkish version for 60-71 month-old children. The universe of the study in which general survey model was used consists of children at 60-71 months of age, who were continuing their education during the spring term of academic year 2017-2018 in public and private kindergartens under the Ministry of National Education within the central district of Aydin/Turkey. As for the sample of the study, 658 children continuing their education in 12 different preschools pre-determined according to socioeconomic status (low-middle-high) were included through systematic sampling method. Validity and reliability studies were carried out using data from the NSS application. Drawing from the analyses, it was determined that item difficulty values of the assessment tool ranged between 0.08 and 0.96, item discrimination indices ranged between 0.17 and 0.53 and item infit and outfit values ranged between 0.50-1.50. Having used Guttman's lambda-2, Alpha coefficient, Feldt-Gilmer coefficient, Feldt-Brennan coefficient and Raju's beta coefficient, it was determined that reliability coefficient calculated for the entire assessment tool varied between 0.826 and 0.837. Following DIF analysis, it was concluded that assessment tool items were not biased towards gender. According to the results of the study, it was concluded that the Turkish version of NSS is a valid and reliable assessment tool for assessing the number sense of children at 60-71 months of age.