Researches reveal that an enduring problem facing MFI is how to attain financial and operationalrnsustainability. Several studies have been conducted to determine the factors affecting the financialrnand operational sustainability of MFIs. However, there are insufficient studies conducted on thisrnarea in Ethiopia. Therefore, this study was conducted to fill the gap. This study is based onrnquantitative research approach using panel data fixed regression as the main data analysisrntechnique. The study was based on a 10 years secondary data obtained from the annual bulletinrnof AEMFI and mix-market database for 13 selected MFIs in Ethiopia. The study found that grantrnto asset ratio, cost per borrower, GDP growth rate, deposit to loan ratio and gross loan portfolio,rnaffects the financial self-sufficiency and sustainability of Ethiopian MFIs significantly. Similarly,rnreturn on asset, experience of MFIs, cost per borrower, portfolio at risk and operating expensernratio affect their operational sustainability. The Study also found that MFIs in Ethiopia arernoperationally self-sufficient while they are not financially self-sufficient. This study recommendsrnmicrofinance institutions to reduce grant to finance their loan, to increase their loan portfolio,rnfind ways of serving the borrowers at the lowest possible cost, increase profitability to raise thernreturn on asset, by making assets operational and minimizing operating expenses.rnKey words: MFIs, sustainability, FSS, OSS, self-sufficiency