<p>Providing effective feedback for student essays has been a longstanding challenge for EFL teachers. Although research has discussed the potentials of generative AI tools in rejuvenating automated writing feedback, few empirical studies have been conducted in authentic educational settings to demonstrate how teachers may collaborate with them in essay evaluation. The present study, adopting the approach of practical action research, examines a teaching assistant’s (TA) experience of employing ChatGPT to enhance teacher feedback in a mainstream college English course in China. Working with an instructor in two action-reflection cycles over a semester, the TA planned, implemented, observed and reflected on AI-assisted teacher feedback for two intermediate-proficiency classes. Data were collected from ChatGPT records, reflective notes, written feedback, student survey and semi-structured interviews to reveal the process and effect of AI-assisted teacher feedback. The first cycle showed that ChatGPT facilitated the TA’s evaluation while introducing new problems and leaving some student needs unaddressed. In the second cycle, a modified use of ChatGPT led to more efficient and satisfactory teacher feedback, yet individualized feedback still remained a longer-term goal. The study proposes a practical framework for integrating generative AI into teacher feedback and underscores the importance of iterative teacher-AI collaboration in advancing sustainable AI-empowered feedback practices.</p>