The study responds to the current issue of integrated learning in preprimary education. It explains concepts in the field of STEM education while elaborating on the teacher’s core competencies for this learning. Although the concept is sufficiently developed, there are still questions in the area of teacher preparedness for this concept. Based on the above facts a literature analysis of research studies dealing with this concept was conducted. The analysis included papers that dealt directly with competencies concerning integrated STEM education. The results show that teachers in many countries do not feel sufficiently competent for STEM education, which may ultimately affect its implementation. Following these results, the paper describes ways to improve teacher training in Slovakia in the field of integrated education.