This paper examines the determinants of inflation for a post communist economy, in the long run as well as in the short run, using time series evidence from Ethiopia and applying the Johnson co integration and Error Correction Mechanisms. A vivid observation of the results shows that the short run determinants of inflation are broad money supply, growth of domestic gross product, real interest rate, budget deficit, Exchange rate, inflation expectation and world price movements. The result of the long run model after co integration is proved using the residual based ducky fuller test and the Johnson co integration tests revealed that broad money supply, government budget deficit, exchange rate and inflation expectation are found to be the major determinants of inflation. The result shows that domestic gross product growth rate has no effect on inflation. To curb inflation, therefore, policy makers need to implement prudential fiscal and monetary policy tools. Inflation expectations need to be tackled by way of transparent and well informed government policies to change consumer perception. Concerning this, it is important to consider targeting monetary and fiscal policy variables and appropriately implanting the set targets.