Conflicts harm the socio-economic and political life of a community. Hence, the inter-ethnicrnconflict between Oromo of Sassiga and Gumuz in Mizhiga districts is an example. The main aimrnof this thesis is to assess the root causes, and consequences of inter-ethnic conflict betweenrnOromo and Gumuz of the study area 2018-2021. A descriptive research design with a mixedrnresearch approach i.e. quantitative and qualitative research approach was employed for thisrnstudy. To achieve the goal, an attempt was made to collect necessary data using a questionnaire,rnin-depth interview, Focus group discussions, and review of written documents. Quantitative datarnwere collected through a questionnaire, interpreted, and presented using the table, andrnpercentage. Whereas, qualitative data that were collected through in-depth interviews and Focusrngroup discussions are presented using descriptive methods. The researcher employed purposivernand simple random sampling techniques to select research participants. The descriptive analysisrnmade shows that the lack of good governance, the proliferation of small weapons, lack of clearrndemarcated boundary, and competition over natural resources as the root causes of inter-ethnicrnconflict between Oromo and Gumuz of the study area. The conflict resulted in economic, social,rnand political crises in the study area. Thus, the study has proved that to bring sustainable peacernin the conflicting area, the administrators of the two districts should give attention to capacityrnbuilding for peace, Advancing good governance, implementation of rule of law, demographicrnpressure of the two ethnic groups of the study area, and demarcating boundary based on thernconsent of the two ethnic groups.