The online flipped classroom has been a growing trend in education, particularly since the Covid-19 pandemic, and now, in the new normal, online learning has become the dominant alternative to traditional learning. In this model of learning, students can prepare new materials through reading or watching lesson videos at home, and then, in the physical or virtual classroom, they have time for active discussions. Although the flipped classroom model has been popular for several decades, the implementation of the flipped classroom in online-based teaching and learning in the context of teaching English as a foreign language (TEFL) has not been widely researched. In this study, an online questionnaire with both closed-ended and open-ended questions was administered to 120 EFL students at a public university in Vietnam, with the aim of understanding EFL students’ perceptions of online flipped learning. The results reveal that students have a relatively positive perception of online flipped learning, although a number of typical challenges can have a negative influence on the effectiveness of this type of instruction. Many suggestions for improving the online flipped classroom were also presented.