In this study, Creative Behavior Observation Form was developed to assess creativity of the children. While the study group on the reliability and validity of Creative Behavior Observation Form was being developed, 257 children in total who were at the ages of 5-6 were used as samples with stratified sampling method. In order to make assessment between the ranges zerofour, a total of 26 items were defined; six items in flexibility dimension, eight items in fluency dimension, six items in originality dimension and five items in elaboration dimensions in line with the literature review and views of the experts. Content Validity Index (CVI) and Confirmatory Factor Analysis (CFA) were applied in order to measure validity of Creative Behavior Observation Form. As a results of confirmatory analysis, it was found out that X2/sd= 3,97, CFI= 0,94 and NNFI= 0,94. Cronbach's Alpha reliability coefficient was calculated in order to ensure reliability of Creative Behavior Observation Form. Coefficient of the form's flexibility factor was calculated as 0,85, fluency factor as 0,88, originality factor as 0,77 and elaboration factor as 0,87. Coefficient for overall Creative Behavior Observation Form was computed to be 0,94. Test-retest method was used in order to determine if Creative Behavior Observation Form has reliable measurements in time. 60 of the 257 children included in the research were randomly selected for this purpose. T-test was used for related samples and Pearson Product Moment Correlation Coefficient of the average values obtained from both application. Correlation coefficient was calculated to be 0,51 as a result of statistical processes. Findings show that Creative Behavior Observation Form can be regarded as a reliable and valid instrument to measure creativity of preschool children. This study concludes with recommendations for the applicators, researchers and teachers who will use Creative Behavior Observation Form as an instrument to develop creativity of preschool children.