This study was conducted to determine the effectiveness of YouTube as supplementary learning to improve students' comprehension of modal verbs. This research was conducted in a high school in the Banyumas region. There are 36 students in experimental group, and 34 students in control group. The statistical test used in this study is the Mann-Whitney test. The results of the Mann-Whitney test showed that the value of Sig.2 tailed is 0.029. Therefore, the test result was not statistically significant. Therefore we can conclude that there is no difference in the distribution of scores on the use of youtube as supplementary learning to improve the students’ comprehension of modal verbs in the experimental class. In terms of the impact of Youtube on the students’ learning habit, more than 80% students of experimental group agreed and gave favorable responses to the questionnaires, indicating that YouTube positively impacted students' study habits.