The educational transition between early childhood education and primary education is a complex moment of change with repercussions throughout the academic life of the students. For this reason, it is important to seek continuity between both educational stages. A successful transition produces for the social, cognitive and emotional well-being of the student. The aim of this study is to find out how transition-related factors apply in ten European Union (EU) countries. The factors analyzed are the age of onset of transition, the teacher–student ratio, types of clustering, financing of the stage, responsibility, and both initial and in-service teacher training. The methodology followed in this study is documentary analysis and the main source of data search has been the European Commission's Eurydice portal. The results show differences in stage change within each country, especially in the explicit consideration of a transition period. The main conclusion is that there is a great difference between the northern and southern countries. The main differences between countries in the transitions from early childhood education to primary education in the EU are in the years of compulsory education, the teacher/student/unit ratio, the initial teacher training, and the decentralization of education.