Abstract: The study aims to examine whether reflective writing using e-portfolios enhances high school students’ self-regulated learning. Participants included two classes of eighth-graders majoring in Information Processing and taking a course called ‘Website Design’ at a vocational high school in Taiwan. There were 41 students, with 18 males and 23 females. The experiment lasted 10 weeks, and students used e-portfolios to reflect on their learning. The results showed that students after using e-portfolios to reflect on their learning had significantly better self-regulated learning than before. This indicates that using e-portfolios for reflection enhanced self-regulated learning. It also shows that high-reflection students had significantly better self-regulated learning than moderate-reflection and low-reflection students, which implies that reflective performance had a significantly positive effect on self-regulated learning.