Expansive soil shows frequent volume changes with the changes in the moisture content, causing severe problems to the civil engineering structures. Consequently, the measurements of swelling properties including free swell index and swelling pressure are extremely important. Several attempts are being made all over the world to control the swell-shrink behavior of expansive soils. Many researches have investigated how to overcome the problems of such soils by means of using different additives such as cement, lime, steel fibers, stone dust and fly ash. This study is directed towards the improvement of expansive soil with a new, inexpensive and environmentally friendly additive. In this study, the effect of using micro silica fume to stabilize the soil was investigated through a laboratory study. Test results showed that, the micro silica fume can considerably decrease the free swell index value by 69% at 25% micro silica fume content. Also, the swelling pressure is reduced from 410 kN/m2 to nearly 330 kN/m2 and 302 kN/m2 at micro silica fume content of 5% and 25%, respectively. This demonstrates the effectiveness of the proposed addition in the expansive soils improvement. This improvement technique can be used in different civil engineering construction projects including slope stabilization and road embankments.