The main objective of investigating the macroeconomic, political, and institutional determinants of private investment in Ethiopia based on a time series data for the period of 1985-2018. ARDL approach to Co-integration was applied in order to investigate the long-run and short-run relationship between dependent and the independent variables. Besides, the study attempted to show the effects of poor governance on private investment growth. The empirical result revealed that real GDP has positive and significant effect on private investment growth in both long run and short run while public investment has a crowding- out effect in short run but crowding- in effect in the long run. Real effective exchange rate has also a positive effect on private investment in long run whereas real interest rate has a significant negative effect on private investment growth in long run unlike its short run effect. In addition, political instability characterized by non-violent protests promotes private investment, while corruption hinders private investment growth. Hence, this study recommends that more effort has to be made to increase the market size and real income of the people to promote private investment. Secondly, public investment in basic infrastructures is crucial to attract private investors though public investment in sectors that compete directly with the private sector retard private investment growth. Thirdly, devaluation of local currencies is not a long-lasting solution to promote private investment. Fourthly, the government has to ensure and take a close monitoring and consistent management strategies to minimize corruption, violent uprisings, and bureaucratic inefficiencies and related governance problems to build up confidence of private investors.