Studies with an explicit focus on dropouts in blended language learning (BLL) are rare and non-existent in the Asian context. This study replicates the early qualitative interview study by Stracke (2007), who explored why foreign language learners drop out of a BLL class. While the 2007 study was carried out in the German higher education context, we conducted this study at a university in Vietnam, where we conducted semi-structured interviews with five students who had left their blended English course after the first semester of study. Our findings indicate that the successful complementarity and integration of the blend components, the crucial role of teacher support and feedback within a learner-centred environment, interactive learning materials, a high level of interaction, and a good relationship between students and teachers are key for students' perception of a successful blended class and retention. The lack of complementarity between the components of the blend remains a major reason for students' dissatisfaction that resulted in them leaving the course in both the 2007 study and this study. Our study allows for a deep understanding of the reasons why Vietnamese EFL students leave a BLL course, thus providing some evidence for pedagogical adjustments for the delivery of current BLL classes in Vietnam and similar contexts. Understanding the reasons why students drop out can help improve the effectiveness of these programs and lead to higher retention rates, a reduction of costs (both financial but also emotional), an increase in student satisfaction, and a better student experience.