The study was conducted to examine the effect of the education program, prepared based on storyline method, on critical thinking skills of five-year-old children. The study was designed using a quantitative model and experimental design. 43 children including 22 in the experimental group and 21 in the control group attending preschool education institutions in the city center of Kirklareli in the school year of 2017-2018 participated in the study. In addition to the existing education programs, the storyline education program was applied by the researcher to the children in the experimental group for 10 weeks (an hour in two days a week) between 19.03.2018 and 22.05.2018. The children in the control group continued their current education programs. In the study, "personal information form" and the "Critical Thinking Skills Test for 5-6 year-old Children (CTTC)" developed by the researcher were used. In the analysis of the data, experimental design with pretest, posttest, retention test, control group was applied to analyze the data. In order to determine the effect of experimental process in cases where the data had normal distribution and homogeneity of the assumptions was provided, two-way ANOVA method was used for mixed patterns that could address the inter-group, intra-group and common effect between the pretest and posttest. In cases where assumptions were not provided, it was examined whether or not posttest and pretest difference scores differed based on the experimental and control groups. For this, independent samples t test was used in the cases where the normality assumption was not provided; whereas, Mann Whitney U test was used for the other situations. It was found as a result of the study that the education program prepared with storyline method made a significant difference in the total score of the critical thinking skills test and in the scores of interpretation, explanation, inference, analysis, and self-regulation subscales of the critical thinking skills test in children in the experimental group. When assessing the effect size of the significance revealed, a high effect size was found in the total score of the critical thinking skills test, an effect size above moderate in the analysis and self-regulation subscales, a moderate effect size in the inference and explanation subscales, and a low effect size quantity in the interpretation subscale.