Using a sociocultural approach, this study investigates how Korean learners of English internalize feedback and how this internalization affects their actual revision. To date, studies on learner response to feedback has used a cognitive approach in which learners are asked about their perceptions of teacher feedback. By adopting the idea of internalization from sociocultural theory, this study complexities analysis by comparing the extent to which two EFL students, Jeong-soo and Jee-min, internalize feedback by conducting in-depth interviews, collecting the written and oral feedback they received on their texts, and collecting the writing assignments they wrote. Analysis reveals that these two students are at different levels of internalization and that this difference is represented in their revisions. This developmental view of learners’ understanding of feedback provides a new perspective on learner response to feedback and implies that writing instructors should not only provide feedback but also facilitate learners’ understanding of feedback so that they can grow into self-regulated learners.