This study explored the impact of self-directed vocabulary learning on the vocabulary and reading abilities of Korean language learners by examining a case study where Korean learners utilized `Google Docs' for their self-learning. To this end, 30 advanced Korean learners, enrolled in academic-purpose Korean courses at undergraduate programs in domestic universities, participated in a 15-week self-directed vocabulary learning program. The learners' vocabulary and reading achievement scores were analyzed based on their task performance using t-tests, simple regression analysis, and Pearson correlation analysis to examine the effectiveness of self-directed vocabulary learning. The results showed that the group that actively engaged in self-directed vocabulary learning scored significantly higher in both vocabulary and reading tests compared to the group that did not (p < .05). Furthermore, self-directed vocabulary learning significantly predicted reading ability, accounting for 15.3% of the variance. These findings highlight the need to create an environment where learners can actively engage in vocabulary learning and the importance of the teachers' encouragement to promote self-directed learning on the learners' behalf. (Ewha womans University)