Expansive soils have shrink and swell properties with moisture variation have difficult engineering properties hence it poses problems during infrastructure development. Soils with desirable engineering properties must be transported from quarries which are many kilometers away. This construction practices require high quality materials to fulfill minimum construction standards which will be transported from long distances from the project site under construction which is costly. In addition, natural resources are degraded and environmentally affecting the quarry areas which has significant environmental effect and this way of construction takes huge amount of budget and is not a sustainable practice. To minimize the cost and alleviate the problem there is a need to develop a cheaper local construction material by improving the geotechnical properties of in-situ materials. Stabilization process has been used to improve the properties of clay soil and helps to attain engineering requirement. Therefore, the main focus of this study is on using bagasse ash as an expansive soil stabilizer. The expansive soil collected from Road segment between Finote Selam and Denbecha town, classified as a CH soil on the USCS classification was stabilized using 4%, 8%, 12%, 16 % and 20% bagasse ash by dry weight of the soil to find out the optimum dosage of stabilizer. Linear shrinkage, Liquid Limit, Plastic Limit, Plastic Index (PI) and Unconfined Compressive Strength (UCS) test samples were air cured for 7 and 14 days before testing. The effect of the Bagasse Ash on the soil was investigated with respect to Free swell index, Linear Shrinkage, plasticity, compaction, Unconfined Compressive Strength (UCS) and California bearing ratio (CBR) tests and from test results it is confirmed that 20 % is an optimum dosage of stabilizer for the typical expansive soil in the study area. The results obtained indicate an increase in optimum moisture content (OMC), Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) while a decrease in maximum dry density (MDD), Free Swell, Linear Shrinkage and plasticity of the soil were observed. Using this optimum dosage of bagasse ash, the improvements are 68.9 %, 47 %, 30.1 %, 94.9 % and 56.9 % respectively for free swell, linear shrinkage, Plastic index, CBR and UCS of the soil.