The purpose of this study is to investigate the effectiveness of using English song to improve students’ vocabulary knowledge. The researcher uses experimental as the design of the research. The researcher followed the equivalent pre-test post-test in two group designs (experimental and control group). To attain the the aim of the study, the researcher distributed pre-test and post-test. The pre-test and post-test are the tools to know the students’vocabulary knowledge. The sample of this study consisted of 50 students (25 students in experimental group and 25 students in control group). The population are eighth grade students in SMP Muhammadiyah 2 Yogyakarta. In experimental and control group the researcher taught four meetings. In experimental group the researcher used English song as the treatment; in the control group the researcher did not used English song. Descriptive statistics analyses use for the pre and post-test for students’ vocabulary test in experimental and control group. Comparison statististical method were used analysis of variance to make a comparison between the experimental and control group. The results of this research indicated that there were significant differences between the mean score of the pre-test and post-test in experimental group and control group. The students’ knowledge in experimental group and control group improved. From the result of paired sample t-test, the significant value was less than the significance level (0.000 < 0.05). It means that there was a significant difference between experimental group and control group. The used of English song has the aspect that can made the students interested. English song made the students enjoy the learning because there is music and lyrics. Therefore, the use of English song effectively improves students’ vocabulary knowledge.