The aim of this study is examine the relationship between school readiness and adaptation problems of primary school first grade students in 2017-2018 academic year. In this study, correlational survey model was used. The sample of the study consists of 909 primary school students studying in İstanbul, Kayseri, Gaziantep and Van provinces determined by stratified purposeful sampling method. In this study, "Primary School Readiness Scale" and "Adaptation to School Scale" were used for data collection. In data analysis, Pearson Product Moment Correlation Coefficient and stepwise regression analysis were used. As a result of the study; a high level, negative and significant relationship was found between school readiness and adaptation problems of primary school students. It was determined that primary school students' readiness concerning affective skills (54.4%), psychomotor skills (4.4%) and cognitive skills (0.5%) accounted for 59.3% of the variance in school adaptation problems of primary school students. It was concluded that students' readiness for self-care skills did not contribute significantly to the variance in school adaptation problems. In this case, it may be advisable to carry out activities such as collaborative learning, drama, role-play and group work to increase students' affective readiness especially in pre-school education and school adaptation curricula.