The existance of smartphone which being a life style nowadays, leads the appear of instant messaging application. One of instant messaging which makes many interest of smartphone users is Line. By the users reach to 400 million in the world makes instant messaging Line takes the popularity in digital native circle which on of them are university student. This research discusses the influence of instant messaging Line usage to the effectiveness of interpersonal communication among the students of Faculty Communication and Business Sciences batch 2011 and 2014. The problem formulation in this research is how the influence use of instant messaging Line to effectiveness of interpersonal communication among students of Communication Sciences Telkom University batch 2011 and 2014. Goals of this study was to determine the influence use of instant messaging Line to the effectiveness of communication among students of Communication Sciences Telkom University batch 2011 and 2014. The methods used is quantitative research with correlation method with survey data collection techniques. Study population is a student of Communication Sciences batch 2011 and 2014 Faculty of Communication and Business, Telkom University which amounts 100 people. The sampling technique used is probability sampling stratified sampling with approach which each batch consists of 35 respondents batch 2011, and 65 respondents batch 2014. Descriptive analysis is used for data analysis technique, Pearson product moment correlation analysis, determination coefficient analysis, simple regression analysis, hypothesis test (t-test), and nor test. The results showed t count amounted to 12.165> 1.985 on table t, then Ho is rejected. That is, there is influence the use of instant messaging Line to effectiveness of interpersonal communication among the students. Contributions influence the use of instant messaging Line to effectiveness of interpersonal communication at 60.2% and the remaining 39.8% is influenced by variables unresearched.