The research investigates the effect of watching YouTube videos on students' second language acquisition based on Krashen (2002). To achieve this aim, this research employs descriptive qualitative method. The data was taken from Junior High School Students in East Barito regency. In collecting data, the researchers used observational method. Students' utterances were observed after watching YouTube's videos. The result of the analysis shows that YouTube's video blogging has effect upon students in SLA. The students get new English vocabulary from various genres of videos. They also improve their English sentence structure found on the video to sentence structure with other words. Video blogging is part of informal environment English as second language acquisition given the benefit in this research so that the student can learn English from different objects, apart from school.