Vocabulary is one of the important elements of the English language. There are many media which can be used in teaching vocabulary to young learners. In this research, the researcher used video on YouTube to teach vocabulary. The research focuses on how students’ engagement during the implementation of video on YouTube in teaching vocabulary at an English course. In this research, the researcher used descriptive–qualitative research, and observation and documentation were used for collecting the data. This research was conducted at an English course in Bogor, in which the participants are seven young learners at grade two. The findings of this research were classified into two themes; students’ response to the classroom activities and the teacher instruction, and student’s engagement to the use of video on YouTube. It is revealed that most young learners at an English course were engaged during the implementation of the video on YouTube in teaching vocabulary. They also gave positive responses to the learning activity and preferred learning English vocabulary by using video on YouTube.