This paper examines The Politics of Opposition in post - 2005 Ethiopia: Challenges and Impacts on Ethiopian Democratic Party (EDP) and Blue Party. 2005 is selected because opposition parties were able to secure more votes than ever before in this election. To address the objectives of the study, the researcher employed qualitative approach with case study design and used primary and secondary data sources. The primary data was collected through semi-structured interviews and secondary sources such as books newspapers, other scholars’ works and different documents also used. The data collected from the primary and secondary data sources were discussed and analyzed thematically based on the emerged themes from participants response. Hence, this case study aimed to explore the experience of these parties in the politics of opposition by focusing on challenges, and impacts in post- 2005 National elections. Blue Party and EDP were selected purposefully since they were active in Ethiopian politics of opposition as national parties. They were also first and second in number of candidatures in 2015 national election but they did not win elections or get representation. Political parties exhibited weakness internally and faced challenges externally. But most opposition parties externalize their overall weakness. This has its impacts on Ethiopian politics of opposition and political process of the country. The study found that opposition parties do have internal and external challenges which affect their activities and do have impacts on political process of the country. Parties are less institutionalized, fragmented, absence of membership commitment and parties’ leaders’ time limit. They also faced challenges from the incumbent party, media and from other institutions of the country. Given research gaps in the domain, this study will help to improve the political culture, democratic system and politics of opposition of the country.