Feedback in online learning is essential to improve both teaching and learning. In peer feedback, students discuss their work and the various problems they encounter in their writing. However, learners may not receive constructive feedback if their classmates have lower writing proficiency. Therefore, anonymous peer feedback training was applied in the writing class to improve the problem of peer feedback during the COVID-19 pandemic. This study first reviews the implementation of peer feedback, particularly with regard to challenges. Subsequently, it describes how anonymous peer feedback is implemented in writing courses. This study explores student attitudes toward anonymous peer feedback and their own ability to provide peer feedback. Meanwhile, it investigates the effect of anonymous peer feedback have on student writing proficiency in the EFL classroom. The 46 participants in this study comprised English department university undergraduates of differing seniority. They attended a weekly 2-hour writing course for a period of 18 weeks. During the experimental teaching, students who participated in anonymous peer feedback-based learning held more positive attitudes toward anonymous peer feedback. Finally, the study discusses student perceptions of anonymous peer feedback in writing courses.