This study investigates the effect of AI-generated feedback on university students’ essay writing proficiency in Hong Kong. By integrating generative AI into the revision process, the research examines how automated feedback influences the quality of students’ written work, as well as their engagement, motivation, and emotional responses during revision. The study employs a randomized controlled design, comparing students who received AI feedback on their essays with those who did not. Both quantitative and qualitative data were collected to assess the impact of AI feedback on writing improvement and student experiences. Quantitative analysis shows significant improvements in essay quality for students who utilized AI feedback, while qualitative findings highlight increased engagement and motivation, though students exhibited mixed emotional responses to the revision process. The results suggest that generative AI has considerable potential to enhance writing skills in higher education by providing timely, individualized feedback. This research contributes to ongoing discussions on the role of AI in education, particularly in supporting language instruction and student development.