The aim of this study was to investigate STEAM (Science, Technology, Engineering, Arts, and Mathematics) teacher education and to examine the successful conditions for its implementation. This study observed two leading schools that have actively participated in STEAM education since the initial stage of STEAM education in Korea. Through participant observation, we videotaped actual lessons, interviewed teachers, and collected their documents. The data analysis was carried out from a community of practice (CoP) perspective and the CoP dimensions were categorized as joint enterprise, mutual engagement, and shared repertoire. The results show that the two communities shared similar dimensions: open-mindedness and self-innovation as joint enterprise, reciprocal relationship and continuous role exchange as mutual engagement, and educational materials and abundant time as shared repertoire. This study gives some practical implications for teachers’ successful engagement with and for their competency in STEAM education.