The study investigates firm-specific determinants of capital structure for a sample of 112 Ethiopian private manufacturing firms using a 10 years panel data for the period of 2005/06 - 2014/15. Random effect regression model was employed in obtaining the numerical estimates of the coefficients. Based on previous empirical studies and theories of capitals structure; firm age, firm size, Profitability, Tangibility, Growth, Liquidity, Non-Debts Tax Shields and Earning volatility were identified as explanatory variables. The result shows that Age, Profitability, Tangibility, Growth, Liquidity and Non-debt tax shield are statistically significant in affecting the capital structure of Ethiopian private manufacturing sector. On the other hand, size and earning volatility are statistically insignificant. In addition, sub-sector classifications were regressed in the independent variable as dummy variables to examine the stability and variability of the regression coefficients across sub sectors.