This study explores the effects of vocabulary notebook keeping under teacher supervision on low-proficiency Korean EFL learners. The participants were randomly divided thus: those who received teacher feedback and had their teacher monitor their notebook use; those who had their teacher only monitor their notebook use; and those who used their notebooks without any teacher intervention. They studied the target words for five weeks, and the results showed that the group that received both teacher feedback and monitoring outperformed the other two in the target vocabulary’s post-test. Furthermore, this difference was maintained two weeks after the post-test as well. The same group was also found to have a more positive attitude toward vocabulary notebook keeping and was more willing to continue keeping a notebook than the other two. These findings point to the important role teachers play in actualizing the full potential of vocabulary notebook keeping.