Mitiku HambisaBitwoded Worku2026-10-062026-10-062026-05https://etd.aau.edu.et/handle/123456789/9070The goal of this research aimed at investigating the relationships among ethnic identity, in-group/out-group bias, and peaceful behavior in Lideta Sub-City, Addis Ababa, Ethiopia. Guided by Social Identity Theory, the study employed cross-sectional design combining quantitative and qualitative approaches methods. A total of 384 youths aged 15 to 29 years were selected through stratified random sampling. Quantitative data were collected using standardized measures of ethnic identity, in-group/out-group bias, and peaceful behavior, while qualitative data were gathered through interviews with youth, religious figures, and traditional institutions leaders. Descriptive statistics, Pearson correlation, and hierarchical multiple regression were used to analyze quantitative data, whereas qualitative data were analyzed thematically. The findings revealed that participants demonstrated relatively high levels of Ethnic identity and peaceful behavior, moderate level of in-group bias, and comparatively low levels of out-group bias. Ethnic identity was positively associated with peaceful behavior, whereas out-group bias showed a strong negative relationship with peaceful behavior. Regression analysis further indicated that ethnic identity significantly and positively predicted peaceful behavior, while out-group bias emerged as the strongest negative predictor. Qualitative findings highlighted the role of religious institutions, traditional community institutions such as Edir, and intergroup interactions in fostering peaceful coexistence, while social media and identity based biases were identified as potential sources of tensions. The study concludes that ethnic identity is not inherently a source of conflict; rather, when grounded in inclusive and cooperative intergroup relations, it can contribute positively to peaceful behavior. Conversely, out-group bias constitutes a major obstacle to peaceful coexistence among youth. The findings underscore the importance of interventions aimed at reducing intergroup bias and strengthening inclusive ethnic identities to promote sustainable peace in multicultural urban settings. Keywords: Ethnic Identity, Social Identity, In-group Bias, Out-group Bias, Peaceful Behavior, YouthenEthnic IdentitySocial IdentityIn-group BiasOut-group BiasPeaceful BehaviorYouthThesis