Although research has ascribed a number of virtues to critical thinking, what critical thinking means is itself open to debate. This paper, as a part of a larger qualitative study on critical thinking practice in a Vietnamese EFL context, presents the findings about how Vietnamese EFL teachers and students in a university interpreted critical thinking. The data were collected through semi-structured interviews with eight teachers and 22 students in a Vietnamese tertiary EFL context to seek their understandings of critical thinking. A majority of the interviews (28) were conducted in Vietnamese, then transcribed in their entirety, and translated into English. Thematic analysis was used to make sense of the data. The participating teachers and students defined critical thinking as involving cognitive skills (e.g., analysing, synthesising, evaluating) and affective dispositions (e.g., inquisitiveness, open-mindedness). Their understandings were found to be limited to the first two domains of criticality in Barnett’s (1997) framework. That is, they understood critical thinking mainly within the domains of “knowledge”, less in “self”, barely at all in the domain of the “world”. The findings further revealed three characteristics distinctive in the participants’ conceptions of critical thinking: (i) expressing personal opinions as an indication of critical thinking, (ii) right/wrong dichotomy as the aim of critical thinking, and (iii) others’ rather than one’s own opinions or arguments as the subject of criticism. The findings imply that the participating teachers and students appeared to have quite a rudimentary grasp of critical thinking and that their understandings were influenced to some extent by the Vietnamese culture of teaching and learning, which has some implications for the application of critical thinking in an EFL context.