The present study examined students' perceptions of immediacy behaviours and credibility of their teachers as well as their willingness to communicate in class, in the South Korean context, with undergraduate English as a Foreign Language (EFL) learners. Participants were 252 undergraduate Korean students enrolled in a mandatory English conversation course, and they were exposed to either native or non-native English-speaking instructors. The two groups exposed to different types of teachers were asked to complete a questionnaire on teacher immediacy, credibility, student willingness to communicate in English, and self-rated English-speaking ability around the end of the semester. Results indicated that sub-components of teacher immediacy and credibility were positively and significantly correlated with each other in both groups. Further, for the participants who had native and non-native English-speaking teachers, different sub-components of teacher immediacy and credibility were found to be related to the participants' willingness to communicate in English during class.