The unreliable contribution of the Ethiopian manufacturing firms on the economic growth is the, main headache to the policy makers in the country. The aims of the study were to identify the determinants of firm growth in Ethiopian manufacturing sector. The study based on data obtained from Ethiopian central statistics agency on medium and large firms for 2008 to 2020. OLS for comparison and System GMM developed by Blundell and Bond (1998) that uses lagged first differences of the explanatory variables and the dependent variable as instruments was used parallel to examine the relationship between size and growth as well as identify the other major determinants of firm growth. Both OLS and system GMM result indicated that age and size have negative relationship with firm growth that shows small and younger firms grow faster. This is good evidence against Gibrat law. Furthermore, the lags of firm growth have negative effect which indicates there is no persistent growth in the Ethiopian medium and large manufacturing firms. In addition export, capital intensity, human capital and location has a positive and significant effect on firm growth while labour productivity has a negative and significant effect on the firm growth. The policy perspective emphasis should be given to improve exposure of firms to foreign market, new technology, and invest on infrastructure and human power development. Small businesses that are more labor-intensive should be more concerned.