Taking cognizance of challenges of 21st century learning and the ubiquitous technologies available, a course applying flipped classroom model with a detailed combination of in-class and out-of-class activities was utilized to teach an academic writing module. The study aimed to (1) find out the effects of flipped classroom model towards improving learners' writing achievements and (2) investigate learners' attitudes towards this approach. 40 English-major freshmen at the Banking University of Ho Chi Minh City, Vietnam participated in the study during the second semester of the 2016-2017 academic year. Both quantitative and qualitative data were collected to ensure the reliability as well as the validity of the results. Analysis of this data revealed that this model was beneficial as it not only improved learners' performance in the final exam but also brought about positive attitudes towards the learning process. Finally, suggestions on how the model could be improved and better utilized are also discussed so that positive learning outcomes in academic essay writing could be obtain.