In spite of the high level of production of sorghum in Ethiopia its threshing and cleaning operations remain among the major challenges to farmers. Efficient sorghum threshers are not available to Ethiopian farmers. To address these problems a sorghum threshing machine was developed. The thresher has a threshing drum of 388 mm diameter and 700 mm length made of an MS flat, having 38 pegs welded in a staggered manner on the drum periphery, which provide impacting and squeezing force to the crop to separate grains from the crop. While the semicircular upper and perforated lower concaves, made of MS sheet and M.S. flats having the opening size of 8 mm, are fitted above and below the threshing drum respectively. Below the lower concave a two-step sieve having mesh size of 6 mm and 5 mm is fitted to facilitate the cleaning action along with the blower which provides a blowing air to the system. The total power requirement of the machine is 2.75 HP / 1.9 KW. The machine’s performance was then evaluated at three levels of drum and blower speeds while feed rate, concave clearance, grain moisture content and drum diameter were kept constant. The results showed that as the drum speed increases, the threshing efficiency increased, the threshing loss reduced, the thresher capacity increased while the unthreshed grain rate reduced. Increase in blower speed increased the cleaning efficiency and the blower loss. The optimum operating condition for the thresher was found to be at drum and blower speed of 640 rpm and 1050 rpm respectively, with total grain loss of 3.05%, throughput capacity of 523.2 kg/hr, cleaning efficiency of 97.20% and threshing efficiency of 96.67%, at feed rate of 720 kg/hr, grain moisture content of 9.4% weight basis and concave clearance of 15mm at inlet and 10 mm at chaff exit.