Reflective functioning is defined as the ability to explain the behavior of others in terms of their mental states (Fonagy & Target, 2005). This ability is derived before the end of the preschool years and it represents one of the crucial changes in child development. This research was conducted on a sample of 60 six-year old children. Readiness for school was operationalized by the Readiness for Elementary School Test -POS (Tolčic, 1986) and children's reflective functioning by one subscale on The Affect task (Steele et al., 1999). Results indicate that children's reflective functioning is a significant predictor of their readiness for school, explaining the 49,4 % of the variance on standardized score of the POS. In detail, results show that children's capacity for reflection explains 63,3% of children's verbal comprehension (beta= ,80), 44% of of variance on logic task (beta= ,67), as 34,9 % (beta=,600) and 37,2% (beta=,619) of the success of children on graphomotor and quantity understanding tasks, respectively. Also, the employment of parents, economic status of a family, higher education of the father and being a firstborn, but not the only child in a the family are factors which are related with children's success on Scholl readiness test. Our results indicate that the system for processing social information is an important predictor of the children's readiness for Elementary school.