Statement of Problem: Although there is a rapidly increasing interest in creativity in specific domains such as science and math, there are not enough valid and reliable scales to assess students' creativity in these domains. If mathematical creativity potential can be measured, then the curriculum can be adapted to address the needs of creative students. In addition to measuring mathematical creativity potential, it is crucial to identify students at as early an age as possible and develop a mathematics curriculum that would complement and supplement their potential (Balka, 1974; Mann, 2005). For these reasons, valid and reliable scales of measurement are necessary for determining the middle school students' (5th, 6th, 7th and 8th grade: 10-15 years old) mathematical creativity. Purpose of the Study: The purpose of this study is to develop a valid and reliable Mathematical Creativity Scale for middle school students (5th, 6th, 7th and 8th grade: 10-15 years old). Method: The main aim of the study is to develop a valid and reliable scale of math creativity for use with middle school students. The pilot study's sample consists of 50 middle school students who attend 5th, 6th, 7th and 8th grades. The field study's sample consists of 297 students who attend 5th, 6th, 7th and 8th grades at 4 middle schools in Istanbul. Exploratory factor analysis (EFA) was applied to evaluate the factor structure of the scale. Item analyses were conducted to check on item discrimination, internal consistency, and agreement between scorers, construct-related validity, and face validity. Findings: Item analysis including the calculation of item discrimination, item total and item remainder values showed that each item was consistent with the entire scale and that distinctive powers of the items were at an acceptable level. To test internal consistency, Cronbach's Alpha coefficient value was found to be 0.80, which supports scale reliability. Since it has a naturally subjective scoring process, the scale was rated by two scorers, and the same scorer re-rated it at a different time. The correlation showed that the scale has an interrater reliability and intrarater reliability. Test-retest coefficient values showed that the scale measurements are consistent. Content, construct and face validity results are presented as a part of validation works of the scale. Acceptability to students' results are also presented. Results: The study results showed that this scale was an appropriate instrument to evaluate middle school (5th, 6th, 7th and 8th grade) students' mathematical creativity. This scale can be used for measurement of the students' creativity in mathematics for the purpose of educational interventions and also for the purpose of determining gifted and talented students in mathematics. [Paper presented at the International Eurasian Educational Research Congress (1st, Istanbul, Turkey, Apr 24-26, 2014).]