This study explored 36 undergraduates' knowledge construction and implementation of pedagogical competence in pronunciation instruction. These undergraduates were language learners themselves, but they were trained to become language teachers receiving pronunciation instruction in an English Pronunciation Instruction course at a university in Taiwan. Data in this study included interview, document, and videos. This study had the following major findings. First, their language competence, knowledge of phonology and pedagogy were constructed in the tertiary course through the instructor's demonstration and their own teaching practice. Secondly, they demonstrated limited knowledge in explicitly explaining pronunciation features to their learners and designing drill practices. They still needed to acquire more knowledge of phonology and pedagogy in order to design communicative tasks for pronunciation practice. A framework on pronunciation instruction to be included in language teacher education was provided.