As one of the university exit requirements and a plus in job applications, the IELTS test has become increasingly popular in Vietnam. Gaining high scores in IELTS is, however, not effortless, especially for those who do not major in English. Many students thus still need coaching and guidance in preparing for IELTS. The outbreak of Covid-19 has normalised online teaching and learning in Vietnam, which used to receive hesitation and even opposition from both teachers and students (Vietnam Economic Times, 2018). The study looks at the delivery of an online IELTS class of nine students to investigate the effectiveness of this mode of instruction, particularly in terms of the students' improved writing skill. To this end, questionnaires and semi-structured interviews were used to elicit the participants' views on the online form of IELTS instruction. The participants' post-tests were analysed quantitatively and qualitatively to assess whether there are any improvements in their writing skill. Preliminary findings revealed overall positive feedback from the participants on the online mode of instruction and areas of improvements that can make online learning a more rewarding experience. However, the study produced mixed results regarding development in the participants' academic writing skill. The findings thus suggest that many different factors determine how effective the online instruction is. Finally, the whole structure of this online instruction including procedures and tools is outlined, and recommendations for upgrading the structure and controlling influencing factors are discussed so that it can be applied successfully in other contexts.