The research, aims to inquire the effectiveness of “Cognitive Development Support Program” applied to 60-72 months old children attending pre-school education institutions, is in experimental design. One of the experimental designs, the pretest-posttest control-group design is used. All 152 students of an independent kindergarten aged 60-72 months in the 2016-2017 academic year at Ataşehir, Istanbul was selected as research population. Four of the children who were found not to have development in expected limits according to applied Denver II Development Screening Test were excluded from the evaluation process. Then, two classes (38 children) were randomly selected as experimental group and two classes (36 children) as control group among eight classes (148 children). Within the scope of the study six data collection tools were used, namely “Personal Information Form,” “Denver II Developmental Screening Test,” “Peabody Picture Vocabulary Test,” “Early Geometry Skill Test,” “Early Numeracy Test - ENT” and “Marmara Primary Education Readiness Scale.” It has been observed in the research that Cognitive Support Program has a positive effect on the language skills, geometry skills and math skills of preschool children but it is similar to that of preschool education program in terms of readiness to primary school.