Social Identity is playing a significant role in influencing people's interactionsrneither in favorable or unfavorable directions. In view of this fact, therefore, thisrnstudy was intended to examine the linkage between social identity andrninterpersonal relationship among Addis Ababa University students as the mainrnobjective. To realize the above set objective different components of social identityrnsuch as gender, ethnicity, and religion were taken as independent variables andrninterpersonal relationship as a dependent variable. Hence, the researcher hasrnset research questions to check whether there is relationship between thernindependent and dependent variables and to determine the prediction power ofrneach predictor variable on the criterion variable. The study was conducted onrn338 (113 of them are females) Third and Fourth year undergraduate regularrnstudents attending their studies at the main campus of Addis Ababa Universityrnduring the Academic Year of 2009/2010. The participants were selected by thernuse of simple random and purposive sampling techniques. The study also reliedrnon quantitative method of data collection and analysis. And the researcher usedrnquestionnaires as a data collection tool. The participants ' social identity wasrnmeasured using a 26 items adapted from Aspects of Identity Questionnairern(Cheek, 2002), and their Interpersonal relationship is also measured by a 26rnitems which was adapted from intergroup interaction scale (Plant, Butz &rnTaratakovsky.2009). The data were analyzed by Pearson Product MomentumrnCorrelation and Step-wise regression statistical techniques analyzed with thernhelp of Statistical package for social scientists (SPSS) version 13. O. The studyrnrevealed that positive and significant relationships were found between allrnindependent variables and the dependent variable. Moreover, gender, ethnic,rnand religious identities were independent significant predictors of interpersonalrnrelationship. However, among the three independent variables ethnicity wasrnfound to be the most prominent determinant of interpersonal relationship amongrnthe subjects. Hence, interpersonal relationship of students was mainlyrndependent on similarity of ethnic background. Finally, the study had suggestedrnsome recommendations to address the identified problems.