Promoting critical thinking (CT) skills has largely attracted the concern of numerous relevant stakeholders, including teachers, students, and policymakers, with the assumption that CT is a vitally learned skill needed by graduates. This study explores the extent of classroom-based assessment strategies used to promote the CT ability of undergraduate students in Vietnam. Qualitative research approaches were employed through in-depth interviews, classroom observations, and assignment analysis with a curriculum review of the Global Citizens Program at Swinburne Vietnam Alliance Program with FPT Education. The findings show that teachers have widely applied a couple of assessment techniques to increase the CT capability of students, including peer review, reflective writing, case study analysis and evaluation, teamwork projects, research-type assessments, and problem-solving. Furthermore, lecturers who are more aware of the importance of CT and those who are more flexible and skilled in testing self-developing techniques have more strategies for incorporating CT into their assessments. The study reveals that if CT is explicitly stated in the program learning outcomes and incorporated into the course outlines, it is more likely to be implemented.