Introduction: Identity as one of the most important components in human and social sciences has gained experts’ attention in recent decades. Identity is a trait that every person chooses. In other words, it is an answer to the question "Who am I? " This is a question that in fact brings struggle to the person. In other words, this “Who”, in contrast to what seems at first glance, is complex and multi-layered. My "Who" may relate to race, ethnicity, gender, religion, age, social class, economic status, Job, membership in Organizations, etc. Identity can be attributed to a combination of these factors with different levels. Hence, what combinations, what hierarchy of layers and in what period can we talk about identity? It depends on many factors, including social possibilities. Social identity has many dimensions that can be placed in a spectrum consists of national, ethical, religious and global identities. One of the factors which has a strong role on shaping people’s identity is cyber space, especially mobile messengers (Telegram, Line, Instagram, and Whats App, etc.). These are apps that allow users to get involved in common activities. Emergence of this technology has brought vast changes in communication among people, and in forming social identities. These technologies provide an opportunity for people to generalize their thoughts and tendencies to real world through these media, so creating a new situation for dialogue and interaction. The purpose of the present paper is to explain students’ social identity indices based on using mobile messenger.Material & Methods: The research method is descriptive-correlative and study population includes all undergraduate students of University of Isfahan in academic year 2016-2017, of whom 338 students were chosen randomly as study sample based on categorized Cochran (1991) formula. To collect data a researcher-made questionnaire was designed. Cronbach's alpha coefficient was calculated at 0.81, while national, ethnic, religious and global identity coefficients were calculated at 0.89, 0.83, 0.76, and 0.87, respectively. Face validity and content validity were analyzed using descriptive statistics (frequency, average, relative frequency and standard deviation), and inferential statistics (t-test, Pearson test and regression analysis).Discussion of Results & Conclusions: Descriptive results showed that 65.8 Percent of undergraduate students used whats App and Telegram, 8.8 Percent use Viber and Line, 19.7 Percent use Instagram, and 6.5 Percent use no messenger app. Out of study sample, 7.7 Percent believe these applications are very important in their daily life, 4.7 Percent would say important, 64.8 Percent to some extent, 13.0 Percent less important and 7.1 percent responded very unimportant. Also, 53.9% of students are 1 – 3 times online, 6.17% of students 4 – 6 times, 8.21% of students 7 – 12 times and 7.6% students are more than 12 times are online daily.38.0% of students have a mobile messenger app for less than one year, 42.6% students for 1 – 2 years, 10.2% for 2 - 3 years and 9.2 % of students have had it for more than 3 years. Also, mobile messenger apps have a negative relationship with national, ethnic, global and religious identities, while students’ attitude towards mobile messenger app can predict and explain 0.6, 0.1, 1.5, 1.7 and 2.2 percent of national, ethnic, religious, global and social identities, respectively. Also, attitude towards these program have negative role on social identity. Therefore, in societies where communications are based on printing media, television and telephone, attitudes can be shaped as beneficial and self-sufficient, but in societies where electronic media are prevalent, attitudes are unstable, scattered and multi-layered. Unfortunately, weak social skills in establishing relations within families and educational institutions, social strains in dialogues, speculation, inner cycle, and luxury life absorb students’ minds and attention to mobile messenger apps. In such a situation, feeling of security declines and student may show risky psychological behaviors.