The study of content and language integrated learning (CLIL) teachers' professional competences remains the most under-researched area in the field of CLIL. To understand the fundamental competences of CLIL teachers, this study investigated the underlying construct of CLIL teacher competences via the systematic analyses of three European CLIL teacher frameworks. It was found that CLIL teachers' professional competences are based on three fundamental aspects: constructive learning, CLIL teaching, and language facilitation. Expressly, CLIL teaching must build on a constructive learning model, primarily focus on learners' learning processes and their understandings, provide the tasks and strategies needed to integrate language use with cognitive thinking, and, finally, provide language acquisition assistance to targeted learners. These findings provide insights for the future establishment of a framework for CLIL teachers' competences in Taiwan.