The main objective of this research is to find out the effectiveness electronic dictionary in learning vocabulary at Indonesian junior high school context. The method employs pre-experimental with pre-test and post-test design, 15 students is involved as the participants of the research. The result of this research reports that there is a significant increase on students’ vocabulary, proven by the value of sig. (2-tailed) is 0.00 0.05. This indicates that H1 is accepted and H0 is rejected. It is assumed that there is a significant difference between the students’ vocabulary after being giving treatment. This is evidenced by the high average students’ post-test score compared to the pre-test, which means it is effective to use electronic dictionary in learning vocabulary.