This study explores non-English major students’ perceptions of the ethical use and plagiarism risks associated with Artificial Intelligence (AI) tools in academic writing at Thu Dau Mot University. As AI technologies become increasingly integrated into higher education, concerns about academic integrity, authorship, and originality have intensified. Using a convergent mixed-methods design, data were collected from 108 students through questionnaires and from six participants via semi-structured interviews. Quantitative findings revealed that a majority of students acknowledged the importance of ethical AI use and expressed support for clearer institutional guidelines and teacher training on responsible AI integration. However, uncertainty persisted regarding the ethical boundaries between legitimate assistance and academic misconduct. Qualitative data reinforced these findings, highlighting students’ awareness of AI’s dual role in enhancing writing skills and posing plagiarism risks, particularly through diminished creativity and loss of personal voice. The study underscores the need for localized policies, updated plagiarism regulations, and pedagogical strategies to guide responsible AI use in EFL writing contexts.