Social media has become an essential platform for teenagers these days. Social media grew in popularity as a means of communication, entertainment, information, and even education, beginning with simple social activities. Today, social media is also a factor in the development of adolescent behaviour. As a result, the purpose of this research is to explore into the language use by teenagers in social media. Over the course of three months, a netnographic approach was employed to study the language use of nine teenagers. All of the participants' postings, whether text, images, or videos, were evaluated. Instagram stories posted, shared, and reposted on the participant's account are also recorded in Nvivo for thematic analysis and coding. The outcomes of the survey highlighted five important themes of the teens' language use and behaviour: entertainment, popularity, morality and ethics, relationships, and new contacts. This study is concluded with some implications and a detailed discussion of adolescent social media language use and behaviour. The outcome of this study is hoped to help to identify problems faced by problematic students, where early prevention or solution can be proposed. Several other recommendations were also proposed at the end of this paper.