The purpose of this study is to explain the use of YouTube channel Cocomelon as a medium for mastery of vocabulary for children aged 4-6 years in Karang Tengah village. This study uses a mixed method, the type of Explanatory Design. The subjects in this study were children aged 4-6 years who live in Karang Tengah Village, Tangerang and their parents who accompany their children to watch YouTube Cocomelon. The sampling technique was nonprobabillity sampling, using purposive sampling type. Collecting data using interview instruments, documentation and non-test instruments. Data analysis used Miles and Huberman's model and descriptive statistics. Based on the results of a questionnaire calculation related to the use of the Cocomelon YouTube Channel as a medium for introducing English vocabulary for children aged 4-6 years in Karang Tengah District, Tangerang, they are included in the "Developing according to expectations" category. This can be seen from the results of the research which states that the average value of children's vocabulary recognition, namely 87.7%, is in the very good category.