Peer feedback has been recognized as a crucial strategy in enhancing L2 writing skills and performance. It addresses common challenges faced by students, such as grammar and spelling errors, limited expression ability, and cultural differences. Peer feed-back and feed-forward are two major approaches to providing peer feedback. However, existing teaching practices overlooked the distinction between peer feed-back and feed-forward, both of which convey different information about students’ learning statuses and may have varying influences on L2 writing. Therefore, this research compared the effects of peer feed-back and peer feed-forward on students’ L2 writing. 44 international students participated in this research and their essays, the results of the domain knowledge understanding test, the content of peer feed-back and peer feed-forward, and self-reported data were collected. Overall, the findings showed that there were no significant differences between peer feed-back and peer feed-forward conditions on students’ L2 writing performance and domain knowledge understanding. Students performed better in producing peer feed-back content than peer feed-forward content. Based on the results, pedagogical implications were proposed to promote peer feedback practices and harness its potentials to improve students’ L2 writing quality.