This study was written with the aim of describing the various impacts caused by mixingIndonesian and English in the interactions of the teenagers in South Jakarta. This study used thesociolinguistic approach because the discussion focuses on the application of English in daily lifewhich has social effects for some people. The problem faced is that there are positive and negativeinfluences from the habits of the teenagers who like to mix the languages they use whilecommunicating. With a qualitative method, this study was designed based on the datas that hadbeen collected from various sources of literature which contain various correlative informationneeded. The results of this study indicate that there are several linguistic factors which encouragethe code mixing phenomenon and it may cause some social effects to the users eventually.