This study explores the integration of the Academic Writing Assistant (AWA), an AI-powered chatbot, in a tertiary-level English as a Foreign Language (EFL) course focused on argumentative writing. Ninety-five third-year students participated in the study, which employed a mixed-methods design comprising questionnaires, reflective journals, and interviews to examine learners’ cognitive, affective, and behavioral engagement. Findings reveal that AWA supported students in organizing ideas, revising drafts, and meeting deadlines. The immediacy and clarity of AI-generated feedback were particularly valued, while concerns about adaptability, data privacy, and reliability were noted. The chatbot contributed to enhanced writing confidence, autonomy, and critical thinking, especially when implemented within ethically guided, instructor-mediated frameworks. The study emphasizes the need for pedagogically sound and ethically responsible approaches to AI-assisted writing instruction in higher education.