This study explores Vietnamese students’ perceptions of Wordtune, an AI-based writing assistant, and investigates the underlying factors that influence these perceptions. Using a mixed-methods approach and the framework from (Verešová and Malá in ICEEPSY 2016: Education and Educational Psychology, 16. European Proceedings of Social and Behavioural Sciences, pp 870–876. Future Academy [1]), the research collected data from a questionnaire and interviews, focusing on three main constructs: affective, behavioral, and cognitive responses to Wordtune. The findings reveal that students generally have positive emotional responses toward the tool, particularly regarding its ability to promote writing autonomy and boost self-confidence. However, students expressed some reservations about its effectiveness for learners at different proficiency levels, with a preference for automated feedback over traditional methods. The study also identifies that while Wordtune is appreciated for its detailed feedback, its use and effectiveness vary based on individual learning needs and familiarity with AI technologies. The results highlight the potential benefits of integrating AI-based writing assistants into educational settings, with recommendations for further improvements to address diverse learner needs.