Biomass energy is the most important primary energy sources in Ethiopia, above 90 % of primary energy comes from biomass.Cow dung is one of the widely consumed biomass as a source of energy in rural areas of Ethiopia in traditional and inefficient cookstoves. The research work was aimed at designing, manufacturing and experimentally testing on its environmental and energy performance as compared to the traditional three-stones stove.In order to design the desired gasifier-cooking stove, ultimate and proximate analyses of dried cow dung were performed to predict the behaviors of fuel. The gasifier reactor is designed and fabricated to meet the cooking energy requirement of five family members by using important parameters that need to be considered in determining the appropriate size of the cow dung gasifier stove. The results from the proximate analysis of cow dung show of60.10% volatile matter, 15.66% ash, 14.35% fixed carbon and 9.88% moisture and its net caloric value is 15.49 MJ/kg and the ultimate analysis of cow dung contains 1.19% N, 41.15% C, 4.21% H, 0.12 % S and 27.76% O. The proposed gasifier shows a better performance than three stones stove when waterboiling test conducted in terms of cooking duration, specific fuel consumption and emission pollutant gases. The experimental results revealed that gasifier stove has shown an increase of thermal efficiency by 26.60 % and reduced PM2.5 and CO emission by 51.01% and 92.67 % respectively as compared to the traditional threestones stove.Furthermore, the gasifier stove has shown 64% fuel saving efficiency as compared to the three stones stove and 54% cooking time saving to cook the same amount and kind of meal.