This study investigates how Quizlet, an online vocabulary learning tool, affects learners' TOEIC scores and their perceptions of learning in a general English course. It also examines whether these effects differ based on learners’ initial proficiency levels. A quasi-experimental design was used with 71 non-English major undergraduates at a regional university in Korea. The control group utilized a paper-based Vocabulary Learning Log (V-log), while the experimental group studied vocabulary using Quizlet.
Data were collected through pre- and post-TOEIC mock tests and a learner perception survey. Paired-samples and independent-samples t-tests were conducted for analysis. The results indicated that both groups made statistically significant improvements in TOEIC scores; however, the experimental group showed greater enhancement with a larger effect size, especially among lower-proficiency learners. Regarding learner perceptions, the experimental group reported more positive feedback in terms of effectiveness, satisfaction, and ease of use, with a statistically significant difference noted in ease of use between the two groups. These findings imply that incorporating an online vocabulary learning tool into a general TOEIC course can enhance learners’ achievements and positively influence their learning experiences. For lower-proficiency learners in particular, early performance improvements may boost engagement and foster a more self-directed approach to learning.